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diff --git a/3679.txt b/3679.txt new file mode 100644 index 0000000..6b0c4dd --- /dev/null +++ b/3679.txt @@ -0,0 +1,5723 @@ +The Project Gutenberg EBook of Getting Gold, by J. C. F. Johnson + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: Getting Gold + +Author: J. C. F. Johnson + +Release Date: April 12, 2006 [EBook #3679] + +Language: English + +Character set encoding: ASCII + +*** START OF THIS PROJECT GUTENBERG EBOOK GETTING GOLD *** + + + + +Produced by Dagny; John Bickers + + + + + +GETTING GOLD: + +A PRACTICAL TREATISE + +FOR PROSPECTORS, MINERS, AND STUDENTS. + + +By J. C. F. Johnson, F. G. S., MEMBER OF THE AUST. INST. OF MINING +ENGINEERS; + +AUTHOR OF "PRACTICAL MINING," "THE GENESIOLOGY OF GOLD," ETC. + + + +PREPARER'S NOTE + +This text was prepared from a 1898 edition, published by Charles Griffin +& Company, Limited; Exeter Street, Strand, London. It is the second +edition, revised. Numerous drawings and diagrams have been omitted. + + + + +PREFACE + +Some six years ago the author published a small book entitled "Practical +Mining," designed specially for the use of those engaged in the always +fascinating, though not as invariably profitable, pursuit of "Getting +Gold." Of this ten thousand copies were sold, nearly all in Australasia, +and the work is now out of print. The London _Mining Journal_ of +September 9th, 1891, said of it: "We have seldom seen a book in which so +much interesting matter combined with useful information is given in so +small a space." + +The gold-mining industry has grown considerably since 1891, and it +appeared to the writer that the present would be a propitious time to +bring out a similar work, but with a considerably enlarged scope. What +has been aimed at is to make "Getting Gold" a compendium, in specially +concrete form, of useful information respecting the processes of winning +from the soil and the after-treatment of gold and gold ores, +including some original practical discoveries by the author. Practical +information, original and selected, is given to mining company +directors, mine managers, quartz mill operators, and prospectors. In +"Rules of Thumb," chapters XI. and XII., will be found a large number +of useful hints on subjects directly and indirectly connected with +gold-mining. + +The author's mining experience extends back thirty years and he +therefore ventures to believe with some degree of confidence that the +information, original or compiled, which the book contains, will be +found both useful and profitable to those who are in any capacity +interested in the gold-mining industry. + +J. C. F. J. + +LONDON, November, 1896. + + + + + +GETTING GOLD + + + +CHAPTER I + +INTRODUCTORY + +GOLD is a name to charm by. It is desired by all nations, and is the one +metal the supply of which never exceeds the demand. Some one has aptly +said, "Gold is the most potent substance on the surface of our planet." +Tom Hood sings: + + Gold, gold, gold, gold! + Bright and yellow, hard and cold; + Molten, graven, hammered, rolled, + Heavy to get, and light to hold; + Stolen, borrowed, squandered, doled. + +That this much appreciated metal is heavy to get is proved by the high +value which has been placed on it from times remote to date, and that it +is light to hold most of us know to our cost. + +We read no farther than the second chapter in the Bible when we find +mention of gold. There Moses speaks of "the land of Havilah, where there +is gold"; and in Genesis, chapter xxiv., we read that Abraham's servant +gave Rebekah an earring of half a shekel weight, say 5 dwt. 13 grs., +and "two bracelets of ten shekels weight," or about 4 1/2 ozs. Then +throughout the Scriptures, and, indeed, in all historic writings, we +find frequent mention of the king of metals, and always it is spoken of +as a commodity highly prized. + +I have sometimes thought, however, that either we are mistaken in the +weights used by the Hebrew nation in early days, or that the arithmetic +of those times was not quite "according to Cocker." We read, I. Kings x. +and xli., that Solomon in one year received no less than six hundred +and three score and six talents of gold. If a talent of gold was, as has +been assumed, 3000 shekels of 219 grains each, the value of the golden +treasure accumulated in this one year by the Hebrew king would have been +3,646,350 pounds sterling. Considering that the only means of "getting +gold" in those days was a most primitive mode of washing it from river +sands, or a still more difficult and laborious process of breaking the +quartz from the lode without proper tools or explosives, and then slowly +grinding it by hand labour between two stones, the amount mentioned is +truly enormous. + +Of this treasure the Queen of Sheba, who came to visit the Hebrew +monarch, contributed a hundred and twenty talents, or, say, 600,000 +pounds worth. Where the Land of Ophir, whence this golden lady came, was +really situated has evoked much controversy, but there is now a general +opinion that Ophir was on the east coast of Africa, somewhere near +Delagoa Bay, in the neighbourhood of the Limpopo and Sabia rivers. It +should be mentioned that the name of the "black but comely" queen was +Sabia, which may or may not be a coincidence, but it is certainly true +that the rivers of this district have produced gold from prehistoric +times till now. + +The discovery of remarkable ruins in the newly acquired province of +Mashonaland, which evince a high state of civilisation in the builders, +may throw some light on this interesting subject. + +The principal value of gold is as a medium of exchange, and its high +appreciation is due, first, to the fact that it is in almost universal +request; and, secondly, to its comparative scarcity; yet, oddly enough, +with the exception of that humble but serviceable metal iron, gold is +the most widely distributed metal known. Few, if any, countries do not +possess it, and in most parts of the world, civilised and uncivilised, +it is mined for and brought to market. The torrid, temperate, and frigid +zones are almost equally auriferous. Siberia, mid-Asia, most parts of +Europe, down to equatorial and southern Africa in the Old World, and +north, central, and southern America, with Australasia, in what may be +termed the New World, are all producers of gold in payable quantities. + +In the earlier ages, the principal source of the precious metal was +probably Africa, which has always been prolific in gold. To this day +there are to be seen in the southern provinces of Egypt excavations and +the remains of old mine buildings and appliances left by the ancient +gold-miners, who were mostly State prisoners. Some of these mines were +worked by the Pharaohs of, and before, the time of Moses; and in these +dreadful places thousands of Israelites were driven to death by the +taskmaster's whip. Amongst the old appliances is one which approximated +very closely to the amalgamating, or blanket table, of a modern quartz +mill. + +The grinding was done between two stones, and possibly by means of such +primitive mechanism as is used to-day by the natives of Korea. + +The Korean Mill is simply a large hard stone to which a rocking motion +is given by manual power by means of the bamboo handles while the ore is +crushed between the upper and basement stone. + +Solomon says "there is no new thing under the sun"; certainly there is +much that is not absolutely new in appliances for gold extraction. I +lately learned that the principle of one of our newest concentrating +machines, the Frue vanner, was known in India and the East centuries +ago; and we have it on good authority--that of Pliny--that gold saving +by amalgamation with mercury was practised before the Christian era. +It will not be surprising then if, ere long, some one claims to have +invented the Korean Mill, with improvements. + +Few subjects in mineralogical science have evoked more controversy than +the origin of gold. In the Middle Ages, and, indeed, down to the time +of that great philosopher, Sir Isaac Newton, who was himself bitten +with the craze, it was widely believed that, by what was known as +transmutation, the baser metals might be changed to gold; and much time +and trouble were expended in attempts to make gold--needless to say +without the desired result. Doubtless, however, many valuable additions +to chemical science, and also some useful metallic alloys, were thus +discovered. + +The latest startling statement on this subject comes from, of course, +the wonderland of the world, America. In a recently published journal it +is said that a scientific metallurgist there has succeeded in producing +absolutely pure gold, which stands all tests, from silver. Needless +to say, if this were true, at all events the much vexed hi-metallic +question would be solved at once and for all time. + +It is now admitted by all specialists that the royal metal, though +differing in material respects in its mode of occurrence from its +useful but more plebeian brethren of the mineral kingdom, has yet been +deposited under similar conditions from mineral salts held in solution. + +The first mode of obtaining this much desired metal was doubtless by +washing the sand of rivers which flowed through auriferous strata. Some +of these, such as the Lydian stream, Pactolus, were supposed to renew +their golden stores miraculously each year. What really happened was +that the winter floods detached portions of auriferous drift from the +banks, which, being disintegrated by the rush and flow of the water, +would naturally deposit in the still reaches and eddies any gold that +might be contained therein. + +The mode of washing was exactly that carried on by the natives in +some districts of Africa to-day. A wooden bowl was partly filled with +auriferous sand and mud, and, standing knee-deep in the stream, the +operator added a little water, and caused the contents of the bowl to +take a circular motion, somewhat as the modern digger does with his tin +dish, with this difference, that his ancient prototype allowed the water +and lighter particles to escape over the rim as he swirled the stuff +round and round. I presume, in finishing the operation, he collected +the golden grains by gently lapping the water over the reduced material, +much as we do now. + +I have already spoken of the mode in which auriferous lode-stuff was +treated in early times--i.e., by grinding between stones. This is also +practised in Africa to-day, and we have seen that the Koreans, with +Mongolian acuteness, have gone a step farther, and pulverise the quartz +by rocking one stone on another. In South America the arrastra is still +used, which is simply the application of horse or mule power to the +stone-grinding process, with use of mercury. + +The principal sources of the gold supply of the modern world have +been, first, South America, Transylvania in Europe, Siberia in Asia, +California in North America, and Australia. Africa has always produced +gold from time immemorial. + +The later development in the Johannesburg district, Transvaal, which has +absorbed during the last few years so many millions of English capital, +is now, after much difficulty and disappointment--thanks to British +pluck and skill--producing splendidly. The yield for 1896 was 2,281,874 +ounces--a yield never before equalled by lode-mining from one field. + +In the year 1847 gold was discovered in California, at Sutor's sawmill, +Sacramento Valley, where, on the water being cut off, yellow specks and +small nuggets were found in the tail race. The enormous "rush" which +followed is a matter of history and the subject of many romances, though +the truth has, in this instance, been stranger than fiction. + +The yield of the precious metal in California since that date up to 1888 +amounts to 256,000,000 pounds. + +Following close on the American discovery came that of Australia, the +credit of which has usually been accorded to Hargraves, a returned +Californian digger, who washed out payable gold at Lewis Ponds Creek, +near Bathurst, in 1851. But there is now no reason to doubt that gold +had previously been discovered in several parts of that great island +continent. It may be news to many that the first gold mine worked in +Australia was opened about twelve miles from Adelaide city, S.A., in the +year 1848. This mine was called the Victoria; several of the Company's +scrip are preserved in the Public Library; but some two years +previous to this a man named Edward Proven had found gold in the same +neighbourhood. + +Most Governments nowadays encourage in every possible way the discovery +of gold-fields, and rewards ranging from hundreds to thousands of pounds +are given to successful prospectors of new auriferous districts. The +reward the New South Wales authorities meted out to a wretched convict, +who early in this century had dared to find gold, was a hundred lashes +vigorously laid on to his already excoriated back. The man then very +naturally admitted that the alleged discovery was a fraud, and that +the nugget produced was a melted down brass candlestick. One would have +imagined that even in those unenlightened days it would not have been +difficult to have found a scientist sufficiently well informed to put a +little nitric acid on the supposed nugget, and so determine whether it +was the genuine article, without skinning a live man first to ascertain. +My belief is that the unfortunate fellow really found gold, but, as Mr. +Deas Thompson, the then Colonial Secretary, afterwards told Hargraves in +discouraging his reported discovery, "You must remember that as soon +as Australia becomes known as a gold-producing country it is utterly +spoiled as a receptacle for convicts." + +This, then, was the secret of the unwillingness of the authorities to +encourage the search for gold, and it is after all due to the fact +that the search was ultimately successful beyond all precedent, +that Australia has been for so many years relieved of the curse of +convictism, and has ceased once and for all to be a depot for the +scoundrelism of Britain--"Hurrah for the bright red gold!" + +Since the year 1851 to date the value of the gold raised in the +Australasian colonies has realised the enormous amount of nearly +550,000,000 pounds. One cannot help wondering where it all goes. + +Mulhall gives the existing money of the world at 2437 million pounds, +of which 846 millions are paper, 801 millions silver, and 790 millions +gold. From 1830 to 1880 the world consumed by melting down plate, etc., +4230 tons of silver more than it mined. From 1800 to 1870 the value of +gold was about 15 1/2 times that of silver. From 1870 to 1880 it was 167 +times the value of silver and now exceeds it over twenty times. In 1700 +the world had 301 million pounds of money; in 1800, 568 million pounds; +and in 1860, 1180 million pounds sterling. + +The gold first worked for in Australia, as in other places, was of +course alluvial, by which is usually understood loose gold in nuggets, +specks, and dust, lying in drifts which were once the beds of long +extinct streams and rivers, or possibly the moraines of glaciers, as in +New Zealand. + +Further on the differences will be mentioned between "alluvial" and +"reef" or lode gold, for that there is a difference in origin in many +occurrences, is, I think, provable. I hold, and hold strongly, that true +alluvial gold is not always derived from the disintegration of lodes or +reefs. For instance, the "Welcome Nugget" certainly never came from a +reef. No such mass of gold, or anything approaching it, has ever yet +been taken from a quartz matrix. It was found at Bakery Hill, Ballarat, +in 1858, weight 2195 ozs., and sold for 10,500 pounds. This was above +its actual value. + +The "Welcome Stranger," a still larger mass of gold, was found amongst +the roots of a tree at Dunolly, Victoria, in 1869, by two starved out +"fossickers" named Deeson and Oates. The weight of this, the largest +authenticated nugget ever found was 2268 1/2 ozs., and it was sold for +10,000 pounds, but it was rendered useless as a specimen by the finders, +who spent a night burning it to remove the adhering quartz. + +But the ordinary digger neither hopes nor expects to unearth such +treasures as these. He is content to gather together by means of +puddling machine, cradle, long tom, or even puddling tub and tin dish, +the scales, specks, dust, and occasional small nuggets ordinarily met +with in alluvial "washes." + +Having sunk to the "wash," or "drift," the digger, by means of one or +more of the appliances mentioned above, proceeds to separate the gold +from the clay and gravel in which it is found. Of course in large +alluvial claims, where capital is employed, such appliances are +superseded by steam puddles, buddles, and other machinery, and sometimes +mercury is used to amalgamate the gold when very fine. Hydraulicing is +the cheapest form of alluvial mining, but can only be profitably carried +out where extensive drifts, which can be worked as quarry faces, and +unlimited water exist in the same neighbourhood. When such conditions +obtain a few grains of gold to the yard or ton will pay handsomely. + +Lode or reef mining, is a more expensive and complicated process, +requiring much skill and capital. First, let me explain what a lode +really is. The American term is "ledge," and it is not inappropriate or +inexpressive. Imagine then a ledge, or kerbstone, continuing to unknown +depths in the earth at any angle varying from perpendicular to nearly +horizontal. This kerbstone is totally distinct from the rocks which +enclose it; those on one side may be slate, on the other, sandstone; but +the lode, separated usually by a small band of soft material known +to miners as "casing," or "fluccan," preserves always an independent +existence, and in many instances is practically bottomless so far as +human exploration is concerned. + +There are, however, reefs or lodes which are not persistent in depth. +Sometimes the lode formation is found only in the upper and newer +strata, and cuts out when, say, the basic rocks (such as granite, etc.) +are reached. Again, there is a form of lode known among miners as a +"gash" vein. It is sometimes met with in the older crystalline slates, +particularly when the lode runs conformably with the cleavage of the +rock. + +Much ignorance is displayed on the subject of lode formation and the +deposition of metals therein, even by mining men of long experience. +Many still insist that lodes, particularly those containing gold, are of +igneous origin, and point to the black and brown ferro-manganic outcrops +in confirmation. It must be admitted that often the upper portions of +a lode present a strong appearance of fire agency, but exactly the same +appearance can be caused by oxidation of iron and manganese in water. + +It may now be accepted as a proven fact that no true lode has been +formed, or its metals deposited except by aqueous action. That is to +say, the bulk of the lode and all its metalliferous contents were once +held in solution in subterranean waters, which were ejected by geysers +or simply filtered into fissures formed either by the shrinkage of the +earth's crust in process of cooling or by volcanic force. + +It is not contended that the effect of the internal fires had no +influence on the formation of metalliferous veins, indeed, it is certain +that they had, but the action was what is termed hydrothermal (hot +water); and such action we may see in progress to-day in New Zealand, +where hot springs stream or spout above the surface, when the silica +and lime impregnated water, reduced in heat and released from pressure, +begins forthwith to deposit the minerals previously held in solution. +Hence the formation of the wondrous Pink and White Terrace, destroyed +by volcanic action some eight years since, which grew almost while +you watched; so rapidly was the silica deposited that a dead beetle or +ti-tree twig left in the translucent blue water for a few days became +completely coated and petrified. + +Gold differs in its mode of occurrence from other metals in many +respects; but there is no doubt that it was once held in aqueous +solution and deposited in its metallic form by electro-chemical action. +It is true we do not find oxides, carbonates, or bromides of gold in +Nature, nor can we feel quite sure that gold now exists naturally as a +sulphide, chloride, or silicate, though the presumption is strongly +that it does. If so, the deposition of the gold may be ceaselessly +progressing. + +Generally reef gold is finer as to size of the particles, and, as a +rule, inferior in quality to alluvial. Thus, in addition to the extra +labor entailed in breaking into one of the hardest of rocks, quartz, +the _madre de oro_ ("mother of gold") of the Spaniards, there is the +additional labour required to pulverise the rock so as to set free the +tiniest particles of the noble metal it so jealously guards. There is +also the additional difficult operation of saving and gathering together +these small specks, and so producing the massive cakes and bars of gold +in their marketable state. + +Having found payable gold in quartz on the surface, the would-be miner +has next to ascertain two things. First, the strike or course of the +lode; and secondly, its underlie, or dip. The strike, or course, is the +direction which the lode takes lengthwise. + +In Australia the term "underlie" is used to designate the angle from +the perpendicular at which the lode lies in its enclosing rocks, and by +"dip" the angle at which it dips or inclines lengthwise on its course. +Thus, at one point the cap of a lode may appear on the surface, and some +distance further the cap may be hundreds of feet below. Usually a shaft +is sunk in the reef to prove the underlie, and a level, or levels, +driven on the course to ascertain its direction underground, also if +the gold extends, and if so, how far. This being proved, next a vertical +shaft is sunk on the hanging or upper wall side, and the reef is either +tapped thereby, or a cross-cut driven to intersect it. + +We will now assume that our miners have found their lode payable, and +have some hundreds of tons of good gold-bearing stone in sight or at the +surface. They must next provide a reducing plant. Of means for crushing +or triturating quartz there is no lack, and every year gives us fresh +inventions for the purpose, each one better than that which preceded +it, according to its inventor. Most practical men, however, prefer to +continue the use of the stamper battery, which is virtually a pestle +and mortar on a large scale. Why we adhere to this form of pulverising +machine is that, though somewhat wasteful of power, it is easily +understood, its wearing parts are cheaply and expeditiously replaced, +and it is so strong that even the most perversely stupid workman cannot +easily break it or put it out of order. + +The stone, being pounded into sand of such degree of fineness as +the gold requires, passes through a perforated iron plate called a +"grating," or "screen," on to an inclined surface of copper plates faced +with mercury, having small troughs, or "riffles," containing mercury, +placed at certain distances apart. + +The crushed quartz is carried over these copper "tables," as they are +termed, thence over the blanket tables--that is, inclined planes covered +with coarse serge, blankets, or other flocculent material--so that the +heavy particles may be caught in the hairs, or is passed over vanners or +concentrating machines. The resulting "concentrates" are washed off from +time to time and reserved for secondary treatment. + +To begin with, they are roasted to get rid of the sulphur, arsenic, +etc., which would interfere with the amalgamation or lixiviation, and +then either ground to impalpable fineness in one of the many triturating +pans with mercury, or treated by chlorine or potassium cyanide. + +If, however, we are merely amalgamating, then at stated periods the +battery and pans are cleaned out, the amalgam rubbed or scraped from +the copper plates and raised from the troughs and riffles. It is then +squeezed through chamois leather, or good calico will do as well, and +retorted in a large iron retort, the nozzle of which is kept in water so +as to convert the mercury vapour again to the metallic form. The result +is a spongy cake of gold, which is either sold as "retorted" gold or +smelted into bars. + +The other and more scientific methods of extracting the precious metal +from its matrices, such as lixiviation or leaching, by means of solvents +(chlorine, cyanogen, hyposulphite of soda, etc.), will be more fully +described later on. + + + +CHAPTER II + +GOLD PROSPECTING--ALLUVIAL AND GENERAL + +It is purposed in this chapter to deal specially with the operation of +searching for valuable mineral by individuals or small working parties. + +It is well known that much disappointment and loss accrue through lack +of knowledge by prospectors, who with all their enterprise and energy +are often very ignorant, not only of the probable locality, mode of +occurrence, and widely differing appearance of the various valuable +minerals, but also of the best means of locating and testing the ores +when found. It is for the information of such as these that this chapter +is mainly intended, not for scientists or miners of large experience. + +All of us who have had much to do with mining know that the majority of +the best mineral finds have been made by the purest accident; often +by men who had no mining knowledge whatever; and that many valuable +discoveries have been delayed, or, when made, abandoned as not payable, +from the same cause--ignorance of the rudiments of mineralogy and +mining. I have frequently been asked by prospectors, when inspecting new +mineral fields, what rudimentary knowledge will be most useful to them +and how it can be best obtained. + +If a man can spare the time a course of lessons at some accredited +school of mines will be, undoubtedly, the best possible training; but +if he asks what books he should read in order to obtain some primary +technical instruction, I reply: First, an introductory text-book of +geology, which will tell him in the simplest and plainest language +all he absolutely requires to know on this important subject. Every +prospector should understand elementary geology so far as general +knowledge of the history of the structure of the earth's crust and of +the several actions that have taken place in the past, or are now in +operation, modifying its conditions. He may with advantage go a few +steps further and learn to classify the various formations into systems, +groups, and series: but he can acquire all that he need absolutely know +from this useful little 2s. 6d. book. Next, it is advisable to learn +something about the occurrence and appearance of the valuable minerals +and the formations in which they are found. For all practical purposes I +can recommend Cox and Ratte's "Mines and Minerals," one of the Technical +Education series of New South Wales, which deals largely with the +subject from an Australian standpoint, and is therefore particularly +valuable to the Australian miner, but which will be found applicable to +most other gold-bearing countries. I must not, however, omit to mention +an admirably compiled _multum in parvo_ volume prepared by Mr. G. +Goyder, jun., Government Assayer and Assay Instructor at the School of +Mines, Adelaide. It is called the "Prospectors' Pocketbook," costs only +one shilling, is well bound, and of handy size to carry. In brief, plain +language it describes how a man, having learned a little of assaying, +may cheaply provide himself with a portable assay plant, and fluxes, and +also gives considerable general information on the subject of minerals, +their occurrence and treatment.[*] + + [*] Another excellent and really practical book is Prof. + Cole's "Practical Aids in Geology" (second edition), 10s. + 6d. + +It may here be stated that some twelve years ago I did a large amount +of practical silver assaying on the Barrier (Broken Hill), which was not +then so accessible a place as it is now, and got closely correct results +from a number of different mines, with an extemporised plant almost +amusing in its simplicity. All I took from Adelaide were a small set of +scales capable of determining the weight of a button down to 20 ozs. to +the ton, a piece of cheese cloth to make a screen or sieve, a tin ring +1 1/2 in. diameter, by 1/2 in. high, a small brass door knob to use as +a cupel mould, and some powdered borax, carbonate of soda, and argol +for fluxes; while for reducing lead I had recourse to the lining of a +tea-chest, which lead contains no silver--John Chinaman takes good care +of that. My mortar was a jam tin, without top or bottom, placed on an +anvil; the pestle a short steel drill. The blacksmith at Mundi Mundi +Station made me a small wrought iron crucible, also a pair of bent tongs +from a piece of fencing-wire. The manager gave me a small common red +flower pot for a muffle, and with the smith's forge (the fire built +round with a few blocks of talcose schist) for a furnace, my plant was +complete. I burned and crushed bones to make my bone-dust for cupelling, +and thus provided made nearly forty assays, some of which were +afterwards checked in Adelaide, in each instance coming as close as +check assays generally do. Nowadays one can purchase cheaply a very +effective portable plant, or after a few lessons a man may by practice +make himself so proficient with the blowpipe as to obtain assay results +sufficiently accurate for most practical purposes. + +Coming then to the actual work of prospecting. What the prospector +requires to know is, first, the usual locality of occurrence of the more +valuable minerals; secondly, their appearance; thirdly, a simple mode +of testing. With respect to occurrence, the older sandy and clay slates, +chlorite slates, micaceous, and hornblendic schists, particularly at or +near their junction with the intrusive granite and diorite, generally +form the most likely geological country for the finding of mineral +lodes, particularly gold, silver and tin. But those who have been +engaged in practical mining for long, finding by experience that no two +mineral fields are exactly alike in all their characteristics, have come +to the conclusion that it is unwise to form theories as to why metals +should or should not be found in certain enclosing rocks or matrices. +Some of the best reef gold got in Victoria has been obtained in dead +white, milky-looking quartz almost destitute of base metal. In South +Australia reef gold is almost invariably associated with iron, either +as oxide, as "gossan;" or ferruginous calcite, "limonite;" or granular +silica, conglomerated by iron, the "ironstone" which forms the capping +or outcrop of many of our reefs, and which is often rich in gold. + +But to show that it is unsafe to decide off-hand in what class of matrix +metals will or will not be found, I may say that in my own experience I +have seen payable gold in the following materials:-- + +Quartz, dense and milky, also in quartz of nearly every colour and +appearance, saccharoidal, crystalline, nay, even in clear glass-like +six-sided prismatic crystals, and associated with silver, copper, lead, +arsenic, iron as sulphide, oxide, carbonate, and tungstate, antimony, +bismuth, nickel, zinc, lead, and other metals in one form or another; +in slate, quartzite, mica schist, granite, diorite, porphyry, felsite, +calcite, dolomite, common carbonate of iron, siliceous sinter from a hot +spring, as at Mount Morgan; as alluvial gold in drifts formed of almost +all these materials; and once, perhaps the most curious matrix of all, +a small piece of apparently alluvial gold, naturally imbedded in a shaly +piece of coal. This specimen, I think, is in the Sydney Museum. One +thing, however, the prospector may make sure of: he will always find +gold more or less intimately associated with silica (Quartz) in one or +other of its many forms, just as he will always find cassiterite (oxide +of tin) in the neighbourhood of granite containing muscovite (white +mica), which so many people will persist in terming talc. It is stated +to be a fact that tin has never been found more than about two miles +from such granite. + +From what has been said of its widely divergent occurrences it will be +admitted that the Cornish miners' saying with regard to metals generally +applies with great force to gold: "Where it is, there it is": and +"Cousin Jack" adds, with pathetic emphasis, "and where it is generally, +there I ain't." + +I have already spoken of the geological "country rock" in which red gold +is most likely to be discovered--i.e., the junction of the slates and +schists with the igneous or metamorphic (altered) rocks, or in +this vicinity. Old river beds formed of gravelly drifts in the same +neighbourhood may probably contain alluvial gold, or shallow deposits of +"wash" on hillsides and in valleys will often carry good surface gold. +This is sometimes due to the denudation, or wearing away, of the hills +containing quartz-veins--that is, where the alluvial gold really was +derived from such veins, which, popular opinion to the contrary, is not +always the case. + +Much disappointment and loss of time and money may sometimes be +prevented if prospectors will realise that _all_ alluvial gold does not +come from the quartz veins or reefs; and that following up an alluvial +lead, no matter how rich, will not inevitably develop a payable +gold lode. Sometimes gold, evidently of reef origin, is found in the +alluvial; but in that case it is generally fine as regards the size +of the particles, more or less sharp-edged, or crystalline in form if +recently shed; while such gold is often of poorer quality than the true +alluvial which occurs in mammillary (breast-like) nuggets, and is of a +higher degree of purity as gold. + +The ordinary non-scientific digger will do well to give credence to +this view of the case, and will often thereby save himself much useless +trouble. Sometimes also the alluvial gold, coarser in size than true +reef-born alluvial, is derived almost _in situ_ from small quartz +"leaders," or veins, which the grinding down of the face of the slates +has exposed; these leaders in time being also broken and worn, set free +the gold they have contained, which does not, as a rule, travel far, but +sometimes becomes water-worn by the rubbing over it of the disintegrated +fragments of rock. + +But the heavy, true alluvial gold, in great pure masses, mammillary, or +botryoidal (like a bunch of grapes) in shape, have assuredly been +formed by accretion on some metallic base, from gold salts in solution, +probably chloride, but possibly sulphide. + +Nuggets, properly so-called, are never found in quartz lodes; but, as +will be shown later, a true nugget having all the characteristics of +so-called water-worn alluvial may be artificially formed on a small +piece of galena, or pyrites, by simply suspending the base metal by a +thread in a vessel containing a weak solution of chloride of gold in +which a few hard-wood chips are thrown. + +Prospecting for alluvial gold at shallow depths is a comparatively easy +process, requiring no great amount of technical knowledge. Usually the +first gold is got at or near the surface and then traced to deep leads, +if such exist. + +At Mount Brown Goldfield, N.S.W., in 1881, I saw claimholders turning +out to work equipped only with a small broom made of twigs and a tin +dish. With the broom they carefully swept out the crevices of the +decomposed slate as it was exposed on the surface, and putting the +resulting dust and fragments into the tin dish proceeded to dry blow it. + +The _modus operandi_ is as follows: The operator takes the dish about +half full of dirt, and standing with his back or side to the wind, if +there be any, begins throwing the stuff up and catching it, or sometimes +slowly pouring it from one dish to another, the wind in either case +carrying away the finer particles. He then proceeds to reduce the +quantity by carefully extracting the larger fragments of rock, till +eventually he has only a handful or so of moderately fine "dirt" which +contains any gold there may be. If in good sized nuggets it is picked +out, if in smaller pieces or fine grains the digger slowly blows the +sand and dust aside with his breath, leaving the gold exposed. This +process is both tedious and unhealthy, and of course can only be carried +out with very dry surface dirt. The stuff in which the gold occurred at +Mount Brown was composed of broken slate with a few angular fragments +of quartz. Yet, strange to say, the gold was invariably waterworn in +appearance. + +Dry blowing is now much in vogue on the West Australian fields owing +to the scarcity of water; but the great objection is first, the large +amount of dust the unfortunate dry blower has to carry about his person, +and secondly, that the peck of dirt which is supposed to last most men a +life time has to be made a continuous meal of every day. + +For wet alluvial prospecting the appliances, besides pick and shovel, +are puddling tub, tin dish, and cradle; the latter, a man handy with +tools can easily make for himself. + +In sinking, the digger should be careful to avoid making his shaft +inconveniently small, and not to waste his energy by sinking a large +"new chum" hole, which usually starts by being about three times too +large for the requirements at the surface, but narrows in like a funnel +at 10 feet or less. A shaft, say 4 feet by 2 feet 6 inches and sunk +plumb, the ends being half rounded, is large enough for all requirements +to a considerable depth, though I have seen smart men, when they were in +a hurry to reach the drift, get down in a shaft even less in size. + +The novice who is trying to follow or to find a deep lead must fully +understand that the present bed of the surface river may not, in fact +seldom does, indicate the ancient watercourses long since buried either +by volcanic or diluvial action, which contain the rich auriferous +deposits for which he is seeking; and much judgment and considerable +underground exploration are often required to decide on the true +course of leads. Only by a careful consideration of all the geological +surroundings can an approximate idea be obtained from surface inspection +alone; and the whole probable conditions which led to the present +contour of the country must be carefully taken into account. + +How am I to know the true bottom when I see it? asks the inexperienced +digger. Well, nothing but long experience and intelligent observation +will prevent mistakes at times, particularly in deep ground; but as a +general rule, though it may sound paradoxical, you may know the bottom +by the top. + +That is, we will assume you are sinking in, say, 10 to 12 feet ground in +a gully on the bank of which the country rock is exposed, and is, say, +for instance, a clay slate or sandy slate set at a certain angle; then, +in all probability, unless there be a distinct fault or change in the +country rock between the slate outcrop and your shaft, the bottom will +be a similar slate, standing at the same angle; and this will +very probably be overlaid by a deposit of pipeclay, formed by the +decomposition of the slates. + +From the crevices of these slates, sometimes penetrating to a +considerable distance, you may get gold, but it is useless attempting to +sink through them. If the outcropping strata be a soft calcareous (limy) +sandstone or soft felspathic rock, and that be also the true bottom, +great care should be exercised or one is apt to sink through the bottom, +which may be very loose and decomposed. I have known mistakes made in +this way when many feet have been sunk, and driven through what was +actually bed rock, though so soft as to deceive even men of experience. +The formation, however, must be the guide, and except in some specially +difficult cases, a man can soon tell when he is really on bed rock or +"bottom." + +On an alluvial lead the object of every one is to "get on the gutter," +that is, to reach the lowest part of the old underground watercourse, +through which for centuries the gold may have been accretionising from +the percolation of the mineral-impregnated water; or, when derived from +reefs or broken down leaders, the flow of water has acted as a natural +sluice wherein the gold is therefore most thickly collected. Sometimes +the lead runs for miles and is of considerable width, at others it is +irregular, and the gold-bearing "gutter" small and hard to find. In many +instances, for reasons not readily apparent, the best gold is not found +exactly at the lowest portion of these narrow gutters, but a little +way up the sides. This fact should be taken into consideration in +prospecting new ground, for many times a claim has been deserted after +cleaning up the "bottom," and another man has got far better gold +considerably higher up on the sides of the gutter. For shallow alluvial +deposits, where a man quickly works out his 30 by 30 feet claim, it may +be cheaper at times to "paddock" the whole ground--that is, take all +away from surface to bottom, but if he is in wet ground and he has to +drive, great care should be taken to properly secure the roof by means +of timber. How this may best be done the local circumstances only can +decide. + + + +CHAPTER III + +LODE OR REEF PROSPECTING + +The preceding chapter dealt more especially with prospecting as carried +on in alluvial fields. I shall now treat of preliminary mining on lodes +or "reefs." + +As has already been stated, the likeliest localities for the occurrence +of metalliferous deposits are at or near the junction of the older +sedimentary formations with the igneous or intrusive rocks, such as +granites, diorites, etc. In searching for payable lodes, whether of +gold, silver, copper, or even tin in some forms of occurrence, the +indications are often very similar. The first prospecting is usually +done on the hilltops or ridges, because, owing to denudation by ice or +water which have bared the bedrock, the outcrops are there more exposed, +and thence the lodes are followed down through the alluvial covered +plains, partly by their "strike" or "trend," and sometimes by other +indicating evidences, which the practical miner has learned to know. + +For instance, a lesson in tracing the lode in a grass covered country +was taught me many years ago by an old prospector who had struck good +gold in the reef at a point some distance to the east of what had been +considered the true course. I asked him why he had opened the ground in +that particular place. Said he, "Some folks don't use their eyes. You +stand here and look towards that claim on the rise where the reef was +last struck. Now, don't you see there is almost a track betwixt here and +there where the grass and herbage is more withered than on either side? +Why? Well, because the hard quartz lode is close to the surface all the +way, and there is no great depth of soil to hold the moisture and make +the grass grow." + +I have found this simple lesson in practical prospecting of use since. +But the strike or course of a quartz reef is more often indicated by +outcrops, either of the silica itself or ironstone "blows," as the +miners call them, but the term is a misnomer, as it argues the easily +disproved igneous theory of veins of ejection, meaning thereby that the +quartz with its metalliferous contents was thrown out in a molten state +from the interior of the earth. This has in no case occurred, and the +theory is an impossible one. True lodes are veins of injection formed +by the infiltration of silicated waters carrying the metals also in +solution. This water filled the fissures caused either by the cooling of +the earth's crust, or formed by sudden upheavals of the igneous rocks. + +Sometimes in alluvial ground the trend of the reef will be revealed by +a track of quartz fragments, more or less thickly distributed on the +surface and through the superincumbent soil. Follow these along, and at +some point, if the lode be continuous, a portion of its solid mass will +generally be found to protrude and can then again be prospected. + +There is no rule as to the trend or strike of lodes, except that a +greater number are found taking a northerly and southerly course than +one which is easterly and westerly. At all events, such is the case in +Australia, but it cannot be said that either has the advantage in being +more productive. Some of the richest mines in Australasia have been in +lodes running easterly and westerly, while gold, tin, and copper, in +great quantity and of high percentage to the ton, have been got in such +mines as Mount Morgan, Mount Bischoff, and the Burra, where there are no +lodes properly so-called at all. + +Mount Morgan is the richest and most productive gold mine in Australasia +and amongst the best in the world. + +Its yield for 1895 was 128,699 oz. of gold, valued at 528,700 pounds. +Dividends paid in 1895, 300,000 pounds. + +This mine was opened in 1886. Up to May 31, 1897, the total yield was +1,631,981 ozs. of gold, sold at 6,712,187 pounds, from which 4,400,000 +pounds have been paid in dividends. (See _Mining Journal_, for Oct. 9, +1897.) + +Mount Morgan shareholders have, in other words, divided over 43 1/2 tons +of standard gold. + +The Burra Burra Mine, about 100 miles from Adelaide, in a direction +a little to the east of north, was found in 1845 by a shepherd named +Pickett. It is singularly situated on bald hills standing 130 feet above +the surrounding country. The ores obtained from this copper mine had +been chiefly red oxides, very rich blue and green carbonates, including +malachite, and also native copper. The discovery of this mine, +supporting, as it did at one time, a large population, marked a new +era in the history of the colony. The capital invested in it was 12,320 +pounds in 5 pound shares, and no subsequent call was ever made upon the +shareholders. The total amount paid in dividends was 800,000 pounds. +After being worked by the original owners for some years the mine was +sold to a new company, but during the last few years it has not been +worked, owing in some degree to the low price of copper and also to the +fact that the deposit then being worked apparently became exhausted. +For many years the average yield was from 10,000 to 13,000 tons of ore, +averaging 22 to 23 per cent of copper. It is stated that, during the +twenty-nine and a half years in which the mine was worked, the company +expended 2,241,167 in general expenses. The output of ore during the +same period amounted to 234,648 tons, equal to 51,622 tons of copper. +This, at the average price of copper, amounted to a money value of +4,749,224 pounds. The mine stopped working in 1877. + +Mount Bischoff, Tasmania, has produced, since the formation of the +Company to December 1895, 47,263 tons of tin ore. It is still in full +work and likely to be for years to come. + +Each of these immense metalliferous deposits was found outcropping on +the summit of a hill of comparatively low altitude. There are no true +walls nor can the ore be traced away from the hill in lode form. These +occurrences are generally held to be due to hydrothermal or geyser +action. + +Then again lodes are often very erratic in their course. Slides and +faults throw them far from their true line, and sometimes the lode is +represented by a number of lenticular (double-pointed in section) masses +of quartz of greater or less length, either continuing point to point or +overlapping, "splicing," as the miners call it. Such formations are very +common in West Australia. All this has to be considered and taken into +account when tracing the run of stone. + +This tyro also must carefully remember that in rough country where the +lode strikes across hills and valleys, the line of the cap or outcrop +will apparently be very sinuous owing to the rises and depressions of +the surface. Many people even now do not understand that true lodes or +reefs are portions of rock or material differing from the surrounding +and enclosing strata, and continuing down to unknown depths at varying +angles. Therefore, if you have a north and south lode outcropping on +a hill and crossing an east and west valley, the said lode, underlying +east, when you have traced its outcrop to the lowest point in the +valley, between the two hills, will be found to be a greater or less +distance, according to the angle of its dip or underlie, to the east of +the outcrop on the hill where it was first seen. If it be followed up +the next hill it will come again to the west, the amount of apparent +deviation being regulated by the height of the hills and depth of the +valley. + +A simple demonstration will make this plain. Take a piece of half-inch +pine board, 2 ft. long and 9 in. wide, and imagine this to be a lode; +now cut a half circle out of it from the upper edge with a fret saw and +lean the board say at an angle of 45 degrees to the left, look along the +top edge, which you are to consider as the outcrop on the high ground, +the bottom of the cut being the outcrop in the valley, and it will be +seen that the lowest portion of the cut is some inches to the right; so +it is with the lode, and in rough country very nice judgment is required +to trace the true course. + +For indications, never pass an ironstone "blow" without examination. +Remember the pregnant Cornish saying with regard to mining and the +current aphorism, "The iron hat covers the golden head." "Cousin Jack," +put it "Iron rides a good horse." The ironstone outcrop may cover a +gold, silver, copper or tin lode. + +If you are searching for gold, the presence of the royal metal should be +apparent on trial with the pestle and mortar; if silver, either by sight +in one of its various forms or by assay, blowpipe or otherwise; copper +will reveal itself by its peculiar colour, green or blue carbonates, red +oxides, or metallic copper. It is an easy metal to prospect for, and +its percentage is not difficult to determine approximately. Tin is more +difficult to identify, as it varies so greatly in appearance. + +Having found your lode and ascertained its course, you want next +to ascertain its value. As a rule (and one which it will be well to +remember) if you cannot find payable metal, particularly in gold "reef" +prospecting, at or near the surface, it is not worth while to sink, +unless, of course, you design to strike a shoot of metal which some one +has prospected before you. The idea is exploded that auriferous lodes +necessarily improve in value with depth. The fact is that the metal in +any lode is not, as a rule, equally continuous in any direction, but +occurs in shoots dipping at various angles in the length of the lode, in +bunches or sometimes in horizontal layers. Nothing but actual exploiting +with pick, powder, and brains, particularly brains, will determine this +point. + +Where there are several parallel lodes and a rich shoot has been found +in one and the length of the payable ore ascertained, the neighbouring +lodes should be carefully prospected opposite to the rich spot, as often +similar valuable deposits will thus be found. Having ascertained that +you have, say, a gold reef payable at surface and for a reasonable +distance along its course, you next want to ascertain its underlie or +dip, and how far the payable gold goes down. + +As a general rule in many parts of Australia--though by no means an +inflexible rule--a reef running east of north and west of south will +underlie east; if west of north and east of south it will go down to the +westward and so round the points of the compass till you come to east +and west; when if the strike of the lodes in the neighbourhood has +come round from north-east to east and west the underlie will be to the +south; if the contrary was the case, to the north. It is surprising how +often this mode of occurrence will be found to obtain. But I cannot too +strongly caution the prospector not to trust to theory but to prove his +lode and his metal by following it down on the underlie. "Stick to your +gold" is an excellent motto. As a general thing it is only when the +lode has been proved by an underlie shaft to water level and explored by +driving on its course for a reasonable distance that one need begin to +think of vertical shafts and the scientific laying out of the mine. + +A first prospecting shaft need not usually be more than 5 ft. by 3 ft. +or even 5 ft. by 2 ft. 6 in., particularly in dry country. One may often +see in hard country stupid fellows wasting time, labour, and explosives +in sinking huge excavations as much as 10 ft. by 8 ft. in solid rock, +sometimes following down 6 inches of quartz. + +When your shaft is sunk a few feet, you should begin to log up the top +for at least 3 ft. or 4 ft., so as to get a tip for your "mullock" +and lode stuff. This is done by getting a number of logs, say 6 inches +diameter, lay one 7 ft. log on each side of your shaft, cut two notches +in it 6 ft. apart opposite the ends of the shaft, lay across it a 5 ft. +log similarly notched, so making a frame like a large Oxford picture +frame. Continue this by piling one set above another till the desired +height is attained, and on the top construct a rough platform and erect +your windlass. If you have an iron handle and axle I need not tell +you how to set up a windlass, but where timber is scarce you may put +together the winding appliance described in the chapter headed "Rules of +Thumb." + +If you have "struck it rich" you will have the pleasure of seeing your +primitive windlass grow to a "whip," a "whim," and eventually to a +big powerful engine, with its huge drum and Eiffel tower-like "poppet +heads," or "derrick," with their great spindle pulley wheels revolving +at dizzy speed high in air. + +"How shall I know if I have payable gold so as to save time and trouble +in sinking?" says the novice. Truly it is a most important part of the +prospector's art, whether he be searching for alluvial or reef gold, +stream or lode tin, copper, or other valuable metal. + +I presume you know gold when you see it? + +If you don't, and the doubtful particle is coarse enough, take a needle +and stick the point into the questionable specimen. If gold the steel +point will readily prick it; if pyrites or yellow mica the point will +glance off or only scratch it. + +The great importance of the first prospect from the reef is well shown +by the breathless intensity with which the two bearded, bronzed pioneer +prospectors in some trackless Australian wild bend over the pan in which +the senior "mate" is slowly reducing the sample of powdered lode stuff. +How eagerly they examine the last pinch of "black sand" in the corner +of the dish. Prosperity and easy times, or poverty and more "hard graft" +shall shortly be revealed in the last dexterous turn of the pan. Let us +hope it is a "pay prospect." + +The learner, if he be far afield and without appliances of any kind, can +only guess his prospect. An old prospector will judge from six ounces of +stuff within a few pennyweights what will be the yield of a ton. I have +seen many a good prospect broken with the head of a pick and panned in +a shovel, but for reef prospecting you should have a pestle and mortar. +The handiest for travelling is a mortar made from a mercury bottle cut +in half, and a not too heavy wrought iron pestle with a hardened face. +To be particular you require a fine screen in order to get your stuff +to regulated fineness. The best for the prospector, who is often on the +move, is made from a piece of cheesecloth stretched over a small hoop. + +If you would be more particular take a small spring balance or an +improvised scale, such as is described in Mr. Goyder's excellent little +book, p. 14, which will enable you to weigh down to one-thousandth of a +grain. It is often desirable to burn your stone before crushing, as +it is thus more easily triturated and will reveal all its gold; but +remember, that if it originally contained much pyrites, unless a similar +course is adopted when treated in the battery, some of the gold will be +lost in the pyrites. + +Having crushed your gangue to a fine powder you proceed to pan it off in +a similar manner to that of washing out alluvial earth, except that in +prospecting quartz one has to be much more particular, as the gold is +usually finer. The pan is taken in both hands, and enough water to cover +the prospect by a few inches is admitted. The whole is then swirled +round, and the dirty water poured off from time to time till the residue +is clean quartz sand and heavy metal. Then the pan is gently tipped, and +a side to side motion is given to it, thus causing the heavier contents +to settle down in the corner. Next the water is carefully lapped in over +the side, the pan being now tilted at a greater angle until the lighter +particles are all washed away. The pan is then once more righted, and +very little water is passed over the pinch of heavy mineral a few times, +when the gold will be revealed in a streak along the bottom. In this +operation, as in all others, only practice will make perfect, and a few +practical lessons are worth whole pages of written instruction. + +To make an amalgamating assay that will prove the amount of gold which +can be got from a ton of your lode, take a number of samples from +different parts, both length and breadth. The drillings from the +blasting bore-holes collected make the best test. When finely triturated +weigh off one or two pounds, place in a black iron pan (it must not be +tinned), with 4 ozs. of mercury, 4 ozs. salt, 4 ozs. soda, and about +half a gallon of boiling water; then, with a stick, stir the pulp +constantly, occasionally swirling the dish as in panning off, till you +feel certain that every particle of the gangue has come in contact with +the mercury; then carefully pan off into another dish so as to lose no +mercury. Having got your amalgam clean squeeze it through a piece of +chamois leather, though a good quality of new calico previously wetted +will do as well. The resulting pill of hard amalgam can then be wrapped +in a piece of brown paper, placed on an old shovel, and the mercury +driven off over a hot fire; or a clay tobacco pipe, the mouth being +stopped with clay, makes a good retort (see "Rules of Thumb," pipe and +potato retorting). The residue will be retorted gold, which, on being +weighed and the result multiplied by 2240 for a 1 lb. assay, or by +1120 for 2 lb., will give the amount of gold per ton which an ordinary +battery might be expected to save. Thus 1 grain to the pound, 2240 lbs. +to the ton, would show that the stuff contained 4 oz. 13 dwt. 8 gr. per +ton. + +If there should be much base metal in your sample such as say +stibnite (sulphide of antimony), a most troublesome combination to the +amalgamator--instead of the formula mentioned above add to your +mercury about one dwt. of zinc shavings or clippings, and to your water +sufficient sulphuric acid to bring it to about the strength of vinegar +(weaker, if anything, not stronger), place your material preferably in +an earthenware or enamelled basin if procurable, but iron will do, and +intimately mix by stirring and shaking till all particles have had an +opportunity to combine with the mercury. Retort as before described. +This device is my own invention. + +The only genuine test after all is the battery, and that, owing to +various causes, is often by no means satisfactory. First, there is a +strong, almost unconquerable temptation to select the stone, thus making +the testing of a few tons give an unduly high average; but more often +the trouble is the other way. The stuff is sent to be treated at some +inefficient battery with worn-out boxes, shaky foundations, and uneven +tables, sometimes with the plates not half amalgamated, or coated with +impurities, the whole concern superintended by a man who knows as little +about the treatment of auriferous quartz by the amalgamating or any +other processes as a dingo does of the differential calculus. Result: +3 dwt. to the ton in the retort, 30 dwt. in the tailings, and a payable +claim declared a "duffer." + +When the lode is really rich, particularly if it be carrying coarse +gold, and owing to rough country, or distance, a good battery is not +available, excellent results in a small way may be obtained by the +somewhat laborious, but simple, process of "dollying." A dolly is a +one man power single stamp battery, or rather an extra sized pestle and +mortar (see "Rules of Thumb"). + +Silver lodes and lodes which frequently carry more or less gold, +are often found beneath the dark ironstone "blows," composed of +conglomerates held together by ferric and manganic oxides; or, where +the ore is galena, the surface indications will frequently be a whitish +limey track sometimes extending for miles, and nodules or "slugs" of +that ore will generally be found on the surface from place to place. +Most silver ores are easily recognisable, and readily tested by means of +the blowpipe or simple fire assay. Sometimes the silver on being tested +is found to contain a considerable percentage of gold as in the great +Comstock lode in Nevada. Ore from the big Broken Hill silver load, New +South Wales, also contains an appreciable quantity of the more precious +metal. A natural alloy of gold containing 20 per cent silver, termed +electrum, is the lowest grade of the noble metal. + +Tin, lode, and stream, or alluvial, occurs only as an oxide, termed +cassiterite, and yet you can well appreciate the compliment one Cornish +miner pays to another whose cleverness he wishes to commend, when he +says of him, "Aw, he do know tin," when you look at a representative +collection of tin ores. In various shapes, from sharp-edged crystals to +mammillary-shaped nuggets of wood-tin; from masses of 30 lbs. weight to +a fine sand, like gunpowder, in colour black, brown, grey, yellow, +red, ruby, white, and sometimes a mingling of several colours, it does +require much judgment to know tin. + +Stream tin is generally associated with alluvial gold. When such is the +case there is no difficulty in saving the gold if you save the tin, for +the yellow metal is of much greater specific gravity. As the natural tin +is an oxide, and therefore not susceptible to amalgamation, the gold can +be readily separated by means of mercury. + +Lode tin sometimes occurs in similar quartz veins to those in which gold +is got, and is occasionally associated with gold. Tin is also found, as +at Eurieowie, in dykes, composed of quartz crystals and large scales +of white mica, traversing the older slates. A similar occurrence +takes place at Mount Shoobridge and at Bynoe Harbour, in the Northern +Territory of South Australia; indeed, one could not readily separate +the stone from these three places if it were mixed. As before stated tin +will never be found far from granite, and that granite must have white +mica as one of its constituents. It is seldom found in the darker +coloured rocks, or in limestone country, but it sometimes occurs in +gneiss, mica schist, and chlorite schist. Numerous other minerals are +at times mistaken for tin, the most common of which are tourmaline or +schorl, garnet, wolfram (which is a tungstate of iron with manganese), +rutile or titanic acid, blackjack or zinc blende, together with +magnetic, titanic, and specular iron in fine grains. + +This rough and ready mode of determining whether the ore is tin is by +weight and by scratching or crushing, when, what is called the "streak" +is obtained. The colour of the tin streak is whitey-grey, which, when +once known, is not easily mistaken. The specific gravity is about 7.0. +Wolfram, which is most like it, is a little heavier, from 7.0 to 7.5, +but its streak is red, brown, or blackish-brown. Rutile is much lighter, +4.2, and the streak light-brown; tourmaline is only 3.2. Blackjack is +4.3, and its streak yellowish-white. + +I have seen several pounds weight to the dish got in some of the New +South Wales shallow sinking tin-fields, and, as a rule, payable gold was +also present. Fourteen years ago I told Western Australian people, when +on a visit to that colony, that the neighbourhood of the Darling range +would produce rich tin. Lately this had been proved to be the case, and +I look forward to a great development of the tin mining industry in the +south-western portion of Westralia. + +The tin "wash" in question may also contain gold, as the country rock of +the neighbourhood is such as gold is usually found in.[*] + + [*] Since this book was in the printers' hands, the + discovery of payable gold has been reported from this + district. A detailed discussion of methods of prospecting + will be found in chapter ii. Of Le Neve Foster's "Ore and + Stone Mining," and Mr. S. Herbert Cox's "Handbook for + Prospectors." + + + + +CHAPTER IV + +THE GENESIOLOGY OF GOLD--AURIFEROUS LODES + +Up to a comparatively recent time it was considered heretical for any +one to advance the theory that gold had been deposited where found by +any other agency than that of fire. As late as 1860 Mr. Henry Rosales +convinced himself, and apparently the Victorian Government also, +that quartz veins with their enclosed metal had been ejected from +the interior of the earth in a molten state. His essay, which is very +ingenious and cleverly written, obtained a prize which the Government +had offered, but probably Mr. Rosales himself would not adduce the +same arguments in support of the volcanic or igneous theory to-day. His +phraseology is very technical; so much so that the ordinary inquirer +will find it somewhat difficult to follow his reasoning or understand +his arguments, which have apparently been founded only on the occurrence +of gold in some of the earlier discovered quartz lodes, and the +conclusions at which he arrived are not borne out by later experience. +He says:--"While, however, there are not apparent signs of mechanical +disturbances, during the long period that elapsed from the cooling +of the earth's surface to the deposition of the Silurian and Cambrian +systems, it is to be presumed that the internal igneous activity of the +earth's crust was in full force, so that on the inner side of it, in +obedience to the laws of specific gravity, chemical attraction, and +centrifugal force, a great segregation of silica in a molten state +took place. This molten silica continually accumulating, spreading, +and pressing against the horizontal Cambro-Silurian beds during a long +period at length forced its way through the superincumbent strata in all +directions; and it is abundantly evident, under the conditions of this +force and the resistance offered to its action, that the line it would +and must choose would be along any continuous and slightly inclined +diagonal, at times crossing the strata of the schists, though generally +preferring to develop itself and egress between the cleavage planes and +dividing seams of the different schistose beds." + +He goes on to say, "Another argument to the same end (i.e., the igneous +origin) may be shown from the fact that the auriferous quartz lodes have +exercised a manifest metamorphic action on the adjacent walls or casing; +they have done so partly in a mineralogical sense, but generally there +has been a metamorphic alteration of the rock." Mr. Rosales then tells +his readers, what we all know must be the case, that the gold would be +volatilised by the heat, as would be also the other metals, which he +says, were in the form of arseniurets and sulphurets; but he fails to +explain how the sublimated metals afterwards reassumed their metallic +form. Seeing that, in most cases, they would be hermetically enclosed in +molten and quickly solidifying silica they could not be acted on to +any great extent by aqueous agency. Neither does Mr. Rosales's theory +account at all for auriferous lodes; which below water level are +composed of a solid mass of sulphide of iron with traces of other +sulphides, gold, calcspar, and a comparatively small percentage of +silica. Nor will it satisfactorily explain the auriferous antimonial +silica veins of the New England district, New South Wales, in which +quantities of angular and unaltered fragments of slate from the +enclosing rocks are found imbedded in the quartz. + +With respect to the metamorphism of the enclosing rocks to a greater +degree of hardness, which Mr. Rosales considered was due to heat, it +should be remembered that these rocks in their original state were much +softer and more readily fusible than the quartz, consequently all would +have been molten and mingled together instead of showing as a rule +clearly defined walls. It is much more rational to suppose that the +increased hardness imparted to the slates and schists at or near their +contact with the lode is due to an infiltration of silica from the +silicated solution which at one time filled the fissure. Few scientists +can now be found to advance the purely igneous theory of lode formation, +though it must be admitted that volcanic action has probably had much +influence not only in the formation of mineral veins, but also on the +occurrence of the minerals therein. But the action was hydrothermal, +just such as was seen in course of operation in New Zealand a few years +ago when, in the Rotomahana district, one could actually see the growing +of the marvellous White and Pink Terraces formed by the release of +silica from the boiling water exuding from the hot springs, which water, +so soon as the heat and pressure were removed, began to deposit its +silica very rapidly; while at the Thames Gold-field, in the same country +hot, silicated water continuously boiled out of the walls of some of +the lodes after the quartz had been removed and re-deposited a siliceous +sinter thereon. + +On this subject I note the recently published opinions of Professor +Lobley, a gentleman whose scientific reputation entitles his utterances +to respect, but who, when he contends that gold is not found in the +products of volcanic action is, I venture to think, arguing from +insufficient premises. Certainly his theories do not hold good either in +Australasia or America where gold is often, nay, more usually, found at, +or near, either present or past regions of volcanic action. + +It is always gratifying to have one's theories confirmed by men whose +opinions carry weight in the scientific world. About seventeen years ago +I first published certain theories on gold deposition, which, even then, +were held by many practical men, and some scientists, to be open to +question. Of late years, however, the theory of gold occurrence by +deposition from mineral salts has been accepted by all but the "mining +experts" who infest and afflict the gold mining camps of the world. +These opine that gold ought to occur in "pockets" only (meaning thereby +their own). + +Recently Professor Joseph Le Conte, at a meeting of the American +Institute of Mining Engineers, criticised a notable essay on the +"Genesis of Ore Deposits," by Bergrath F. Posepny. The Professor's +general conclusions are: + +1. "Ore deposits, using the term in its widest sense, may take place +from any kinds of waters, but especially from alkaline solutions, for +these are the natural solvents of metallic sulphides, and metallic +sulphides are usually the original form of such deposits." + +2. "They may take place from waters at any temperature and any pressure, +but mainly from those at high temperature and under heavy pressure, +because, on account of their great solvent power, such waters are +heavily freighted with metals." + +3. "The depositing waters may be moving in any direction, up-coming, +horizontally moving, or even sometimes down-going, but mainly up-coming; +because by losing heat and pressure at every step such waters are sure +to deposit abundantly." + +4. "Deposits may take place in any kind of waterways--in open fissures, +in incipient fissures, joints, cracks, and even in porous sandstone, but +especially in great open fissures, because these are the main highways +of ascending waters from the greatest depths." + +5. "Deposits may be found in many regions and in many kinds of rocks, +but mainly in mountain regions, and in metamorphic and igneous rocks, +because the thermosphere is nearer the surface, and ready access thereto +through great fissures is found mostly in these regions and in these +rocks." + +These views are in accordance with nearly all modern research into this +interesting and fruitful subject. + +Among the theories which they discredit is that ore bodies may usually +be assumed to become richer in depth. As applied to gold lodes the +teaching of experience does not bear out this view. + +If it be taken into account that the time in which most of our +auriferous siliceous lodes were formed was probably that indicated in +Genesis as before the first day or period when "the earth was without +form and void, and darkness was upon the face of the deep," it will be +realised that the action we behold now taking place in a small way in +volcanic regions, was probably then almost universal. The crust of the +earth had cooled sufficiently to permit water to lie on its surface, +probably in hot shallow seas, like the late Lake Rotomahana. Plutonic +action would be very general, and volcanic mud, ash, and sand would be +ejected and spread far and wide, which, sinking to the bottom of the +water, may possibly be the origin of what we now designate the azoic or +metamorphic slates and schists, as also the early Cambrian and Silurian +strata. These, from the superincumbent weight and internal heat, became +compacted, and, in some cases, crystallised, while at the same time, +from the ingress of the surface waters to the heated regions below, +probably millions of geysers were spouting their mineral impregnated +waters in all directions; and in places where the crust was thin, +explosions of super-heated steam caused huge upheavals, rifts, and +chasms, into which these waters returned, to be again ejected, or to +be the cause of further explosions. Later, as the cooling-process +continued, there would be shrinkages of the earth's crust causing other +fissures; intrusive granites further dislocated and upheaved the slates. +About this age, probably, when really dry land began to appear, came the +first formation of mineral lodes, and the waters, heavily charged with +silicates, carbonates of lime, sulphides, etc., in solution, commenced +to deposit their contents in solid form when the heat and pressure were +removed. + +I am aware that part of the theory here propounded as to the probable +mode of formation of the immense sedimentary beds of the Archaic or +Azoic period is not altogether orthodox--i.e., that the origin of +these beds is largely due to the ejection of mud, sand, and ashes from +subterraneous sources, which, settling in shallow seas, were afterwards +altered to their present form. It is difficult, however, to believe that +at this very early period of geologic history so vast a time had elapsed +as would be required to account for these enormous depositions of +sediment, if they were the result only of the degradation of previously +elevated portions of the earth's surface by water agency. Glacial action +at that time would be out of the question. + +But what about the metals? Whence came the metallic gold of our reefs +and drifts? What was it originally--a metal or a metallic salt, and if +the latter, what was its nature?--chloride, sulphide, or silicate, one, +or all three? I incline to the latter hypothesis. All three are known, +and the chemical conditions of the period were favorable for their +natural production. Assuming that they did exist, the task of +accounting for the mode of occurrence of our auriferous quartz lodes is +comparatively simple. Chloride of gold is at present day contained in +sea water and in some mineral waters, and would have been likely to be +more abundant during the Azoic and early Paleozoic period. + +Sulphide of gold would have been produced by the action of sulphuretted +hydrogen; hence probably our auriferous pyrites lodes, while silicate +of gold might have resulted from a combination of gold chlorides with +silicic acid, and thus the frequent presence of gold in quartz is +accounted for. + +A highly interesting and instructive experiment, showing how gold might +be, and probably was, deposited in quartz veins, was carried out by +Professor Bischof some years ago. He, having prepared a solution of +chloride of gold, added thereto a solution of silicate of potash, +whereupon, as he states, the yellow colour of the chloride disappeared, +and in half an hour the fluid turned blue, and a gelatinous dark-blue +precipitate appeared and adhered to the sides of the vessel. In a +few days moss-like forms were seen on the surface of the precipitate, +presumably approximating to what we know as dendroidal gold--that +is, having the appearance of moss, fern, or twigs. After allowing the +precipitate to remain undisturbed under water for a month or two a +decomposition took place, and in the silicate of gold specks of metallic +gold appeared. From this, the Professor argues, and with good show of +reason, that as we know now that the origin of our quartz lodes was +the silicates contained in certain rocks, it is probable that a natural +silicate of gold may be combined with these silicates. If this can be +demonstrated, the reason for the almost universal occurrence of gold in +quartz is made clear. + +About 1870, Mr. Skey, analyst to the New Zealand Geological Survey +Department, made a number of experiments of importance in respect to +the occurrence of gold. These experiments were summarised by Sir James +Hector in an address to the Wellington Philosophical Society in 1872. +Mr. Skey's experiments disproved the view generally held that gold is +unaffected by sulphur or sulphuretted hydrogen gas, and showed that +these elements combined with avidity, and that the gold thus treated +resisted amalgamation with mercury. Mr. Skey proved the act of +absorption of sulphur by gold to be a chemical act, and that electricity +was generated in sufficient quantity and intensity during the process +to decompose metallic solutions. Sulphur in certain forms had long been +known to exercise a prejudicial effect upon the amalgamation of gold, +but this had always been attributed to the combination of the sulphur +with the quicksilver used. Now, however, it is certain that the +sulphurising of the gold must be taken into account. We must remember +that the particles of gold in the stone may be enveloped with a film +of auriferous sulphide, by which they are protected from the solvent +actions of the mercury. The sulphurisation of the gold gives no ocular +manifestation by change of colour or perceptible increase of weight, +as in the case of the formation of sulphides of silver, lead and other +metals, on account of the extremely superficial action of the sulphur, +and hence probably the existence of the gold sulphide escaped detection +by chemists. + +Closely allied to this subject is the investigation of the mode in which +certain metals are reduced from their solutions by metallic sulphides, +or, in common language, the influence which the presence of such +substances as mundic and galena may exercise in effecting the deposit +of pure metals, such as gold, in mineral lodes. The close relation which +the richness of gold veins bears to the prevalence of pyrites has been +long familiar both to scientific observers and to practical miners. The +gold is an after deposit to the pyrites, and, as Mr. Skey was the +first to explain, due to its direct reducing influences. By a series of +experiments Mr. Skey proved that the reduction of the metal was due to +the direct action of the sulphide, and showed that each grain of iron +pyrites, when thoroughly oxidised, will reduce 12 1/4 grains of gold +from its solution as chloride. He also included salts of platina and +silver in this general law, and demonstrated that solutions of any of +these metals traversing a vein rock containing certain sulphides would +be decomposed, and the pure metal deposited. We are thus enabled to +comprehend the constant association of gold, or native alloys of gold +and silver, in veins which traverse rocks containing an abundance +of pyrites, whether they have been formed as the result of either +sub-aqueous volcanic outburst or by the metamorphism of the +deeper-seated strata which compose the superficial crust of the earth. + +Mr. Skey also showed by very carefully conducted experiments that the +metallic sulphides are not only better conductors of electricity than +has hitherto been supposed, but that when paired they were capable of +exhibiting strong electro-motive power. Thus, if galena and zinc blende +in acid solutions be connected in the usual manner by a voltaic pair, +sulphuretted hydrogen is evolved from the surface of the former, and a +current generated which is sufficient to reduce gold, silver or copper +from their solutions in coherent electro-plate films. The attributing +of this property of generating voltaic currents, hitherto supposed to +be almost peculiar to metals, to such sulphides as are commonly found +in metalliferous veins, further led Mr. Skey to speculate how far the +currents discovered to exist in such veins by Mr. E. F. Fox might be +produced by the gradual oxidation of mixed sulphides, and that veins +containing bands of different metallic sulphides, bounded by continuing +walls, and saturated with mineral waters, may constitute under +some circumstances a large voltaic battery competent to produce +electro-deposition of metals, and that the order of the deposit of these +mineral lodes will be found to bear a definite relation to the order +in which the sulphides rank in the table of their electro-motive power. +These researches may lead to some clearer comprehension of the law which +regulates the distribution of auriferous veins, and may explain why in +some cases the metal should be nearly pure, while in others it is so +largely alloyed with silver. + +The following extract was lately clipped from a mining paper. If true, +the experiment is interesting:-- + +"An American scientist has just concluded a very interesting and +suggestive experiment. He took a crushed sample of rich ore from Cripple +Creek, which carried 1100 ozs. of gold per ton, and digested it in a +very weak solution of sodium chloride and sulphate of iron, making +the solution correspond as near as practicable to the waters found in +Nature. The ore was kept in a place having a temperature little less +than boiling water for six weeks, when all the gold, except one ounce +per ton, was found to have gone into solution. A few small crystals of +pyrite were then placed in the bottle of solution, and the gold began +immediately to precipitate on them. It was noticeable, however, that the +pyrite crystals which were free from zinc, galena, or other extraneous +matter received no gold precipitate. Those which had such foreign +associations were beautifully covered with fine gold crystals." + +Experimenting in a somewhat similar direction abut twelve months since, +I found that the West Australian mine water, with the addition of an +acid, was a solvent of gold. The idea of boiling it did not occur to me, +as the action was rapid in cold water. + +Assuming, then, that gold originally existed as a mineral salt, when and +how did it take metallic form? Doubtless, just in the same manner as +we now (by means of well-known reagents which are common in nature) +precipitate it in the laboratory. With regard to that found in quartz +lodes finely disseminated through the gangue, the change was brought +about by the same agency which caused the silicic acid to solidify and +take the form in which we now see it in the quartz veins. Silica is +soluble in solutions of alkaline carbonates, as shown in New Zealand +geysers; the solvent action being increased by heat and pressure, so +also would be the silicate or sulphide of gold. When, however, the +waters with their contents were released from internal pressure and +began to lose their heat the gold would be precipitated together with +the salts of some other metals, and would, where the waters could +percolate, begin to accretionise, thus forming the heavy or specimen +gold of some reefs. On this class of deposition I shall have more to say +when treating of the origin of alluvial gold in the form of nuggets. + +Mr. G. F. Becker, of the United States Geological Survey, writing of +the geology of the Comstock lode, says:--"Baron Von Richthofen was of +opinion that fluorine and chlorine had played a large part of the ore +deposition in the Comstock, and this the writer is not disposed to +deny; but, on the other hand, it is plain that most of the phenomena are +sufficiently accounted for on the supposition that the agents have been +merely solutions of carbonic and hydro-sulphuric acids. These reagents +will attack the bisilicates and felspars. The result would be carbonates +and sulphides of metals, earth, alkalies, and free quartz, but quartz +and sulphides of the metals are soluble in solutions of carbonates and +sulphides of the earths and alkalies, and the essential constituents of +the ore might, therefore, readily be conveyed to openings in the +vein where they would have been deposited on relief of pressure and +diminution of temperature. An advance boring on the 3000 ft. level of +the Yellow Jacket struck a powerful stream of water at 3065 ft. (in the +west country), which was heavily charged with hydrogen sulphide, and +had a temperature of 170 degrees F., and there is equal evidence of the +presence of carbonic acid in the water of the lower levels. A spring on +the 2700 ft. level of the Yellow Jacket which showed a temperature +of about 150 degrees F., was found to be depositing a sinter largely +composed of carbonates." + +It may be worth while here to speak of the probable reason why gold, and +indeed almost all the metals generally occur in shutes in the lodes; and +why, as is often the case, these shutes are found to be more or less in +a line with each other in parallel lodes, and why also the junction of +two lodes is frequently specially productive. The theory with respect +to these phenomena which appears most feasible is, that at these points +certain chemical action has taken place, by which the deposition of the +metals has been specially induced. Generally a careful examination of +the enclosing rocks where the shute is found will reveal some points of +difference from the enclosing rocks at other parts of the course of the +lode, and when ore shutes are found parallel in reefs running on the +same course, bands or belts of similar country rock will be found at the +productive points. From this we may fairly reason that at these points +the slow stream filling the lode cavity met with a reagent percolating +from this particular band of rock, which caused the deposition of +its metals; and, indeed, I am strongly disposed to believe that the +deposition of metals, particularly in some loose lodes, may even now be +proceeding. But as in Nature's laboratory the processes, if certain, are +slow, this theory may be difficult to prove. + +Why the junction of lodes is often found to be more richly metalliferous +than neighbouring parts is probably because there the depositing +reagents met. This theory is well put by Mr. S. Herbert Cox, late of +Sydney, in his useful book, "Mines and Minerals." He says:--"It is a +well-known fact in all mining districts that the junctions of lodes are +generally the richest points, always supposing that this junction takes +place in 'kindly country,' and the explanation of this we think is +simple on the aqueous theory of filling of lodes. The water which is +traversing two different channels of necessity passes through different +belts of country, and will thus have different minerals in solution. As +a case in point, let us suppose that the water in one lode contained in +solution carbonates of lime, and the alkalies and silica derived form +a decomposition of felspars; and that the other, charged with +hydro-sulphuric acid, brought with it sulphide of gold dissolved in +sulphide of lime. The result of these two waters meeting would be that +carbonate of lime would be formed, hydro-sulphuric acid would be set +free, and sulphide of gold would be deposited, as well as silica, which +was formerly held in solution by the carbonic acid." + +Most practical men who have given the subject attention will, I think, +be disposed to coincide with this view, though there are some who hold +that the occurrence of these parallel ore shutes and rich deposits at +the junctions of lodes is due to extraneous electrical agency. Of this, +however I have failed to find any satisfactory evidence. + +There is, however, proof that lodes are actually re-forming and the +action observed is very interesting as showing how the stratification +in some lodes has come about. Instances are not wanting of the growth of +silica on the sides of the drives in mines. This was so in some of the +mines on the Thames, New Zealand, previously mentioned, where in some +cases the deposition was so rapid as to be noticeable from day to day, +whilst the big pump was actually choked by siliceous deposits. In old +auriferous workings which have been under water for years, in many parts +of the world, formations of iron and silica have been found on the +walls and roof, while in mining tunnels which have been long unused +stalactites composed of silica and calcite have formed. Then, again, +experiments made by the late Professor Cosmo Newbery, in Victoria, +showed that a distinctly appreciable amount of gold, iron, and silica +(the latter in granular form) could be extracted from solid mine timber; +which had been submerged for a considerable time. + +This reaction then must be in progress at the present time, and +doubtless under certain conditions pyrites would eventually take +the place of the timber, as is the case with some of the long buried +driftwood found in Victorian deep leads. Again, we know that the water +from some copper mines is so charged with copper sulphate that if scrap +iron be thrown into it, the iron will be taken up by the sulphuric acid, +and metallic copper deposited in its place. All this tends to prove that +the deposition of metals from their salts, though probably not now +as rapid as formerly, is still ceaselessly going on in some place or +another where the necessary conditions are favourable. + +With regard to auriferous pyritic lodes, it does not appear even now to +be clear, as some scientists assert, that their gold is never found +in chemical combination with the sulphides of the base metals. On the +contrary, I think much of the evidence points in the other direction. + +I have long been of opinion that it is really so held in many of the +ferro-sulphides and arsenio-ferro sulphides. On this subject Mr. T. +Atherton contributed a short article in 1891 to the _Australian Mining +Standard_ which is worthy of notice. He says, referring to an occurrence +of a Natural Sulphide of Gold: "The existence of gold, in the form of +a natural sulphide in conjunction with pyrites, has often been advanced +theoretically, as a possible occurrence; but up to the present time +has, I believe, never been established as an actual fact. During my +investigation on the ore of the Deep Creek mines, Nambucca, New South +Wales, I have found in them what I believe to be gold existing as a +natural sulphide. The lode is a large irregular one of pure arsenical +pyrites carrying, in addition to gold and silver, nickel and cobalt. It +exists in a felsite dyke immediately on the coast. Surrounding it on all +sides are micaceous schists, and in the neighbourhood about half a mile +distant is a large granite hill about 800 feet high. In the lode and its +walls are large quantities of pyro-phyllite, and in some parts of the +mine there are deposits of pure white translucent mica, but in the ore +itself it is a yellow or pale olive green, and is never absent from the +pyrites. + +"From the first I was much struck with the exceedingly fine state of +division in which the gold existed in the ore. After roasting and very +carefully grinding down in an agate mortar, I have never been able to +get any pieces of gold exceeding one-thousandth of an inch in diameter, +and the greater quantity is very much finer than this. Careful +dissolving of the pyrites and gangue so as to leave the gold intact +failed to find it in any larger diameter. As this was a very unusual +experience in investigations on many other kinds of pyrites, I was led +further into the matter. + +"Ultimately, after a number of experiments, there was nothing left but +to test for gold existing as a natural sulphide. Taking 200 gr. of ore +from a sample assaying 17 oz. fine gold per ton, grinding it finely and +heating for some hours with yellow sodium sulphide--on decomposing the +filtrate and treating for gold I got a result at the rate of 12 oz. per +ton. This was repeated several times with the same result. + +"This sample came from the lode at the 140 ft. level, whilst samples +from the higher levels where the ore is more oxidised, although carrying +the gold in exactly the same degree of fineness, do not give as high a +percentage of auric sulphide. + +"It would appear that all the gold in the pyrites (and I have never +found any gold existing apart from the pyrites) has originally taken its +place there as a sulphide." + +Professor Newbery, who made many valuable suggestions on the subject, +says, speaking of gold in pyritous lodes: + +"As it (the gold salt) may have been in the same solution that +deposited the pyrites, which probably contained its iron in the form of +proto-carbonate with sulphates, it was not easy at first to imagine any +ordinary salt of gold; but this I find can be accomplished with very +dilute solutions in the presence of an alkaline carbonate and a large +excess of carbonic acid, both of which are common constituents of +mineral waters, especially in Victoria. This is true of chloride of +gold, and if the sulphide is required in solution, it is only necessary +to charge the solution with an excess of sulphuretted hydrogen. In this +matter both sulphides may be retained in the same solution, depositing +gradually with the escape of the carbonic acid." + +Pyritic lodes usually contain a considerable proportion of calcareous +matter, mostly carbonates, and consequently it appears not improbable +that the gold may remain in some instances as a sulphide, particularly +in samples of pyrites, in which it cannot be detected even by the +microscope until by calcination the iron sulphide is changed to an +oxide, wherein the gold may be seen in minute metallic specks. The whole +subject is full of interest, and careful scientific investigation may +lead to astonishing results. + + + +CHAPTER V + +THE GENESIOLOGY OF GOLD--AURIFEROUS DRIFTS + +Having considered the origin of auriferous lodes, and the mode by which +in all probability the gold was conveyed to them and deposited as a +metal, it is necessary also to inquire into the derivation of the gold +of our auriferous drifts, and the reasons for its occurrence therein. + +When quite a lad on the Victorian alluvial fields, I frequently heard +old diggers assert that gold grew in the drifts where found. At the time +we understood this to mean that it grew like potatoes; and, although not +prepared with a scientific argument to prove that such was not so, the +idea was generally laughed at. I have lived to learn that these old +hard-heads were nearer the truth than possibly they clearly realised, +and that gold does actually grow or agglomerate; and, indeed, is +probably even now thus growing, though it is likely that the chemical +and electric action in the mineral waters flowing through the drifts is +not in this age nearly so active as formerly. + +Most boys have tried the experiment of dipping a clean-bladed knife into +sulphate of copper, and so depositing on the steel a film of copper, +which adheres closely until worn away. This is a simple demonstration +of a hydro-metallurgical process, though probably young hopeful is not +aware of the fact; and it is really by an enlargement of this process +that our beautiful and artistic gold-and silver-plated ware is produced. + +In the great laboratory of Nature similar chemical depositions have +taken place in the past, and may still be in progress; indeed, there is +sound scientific reason to suppose that in certain localities this is +even now the case, and that in this way much of our so-called alluvial +gold has been formed, that is, by the deposition on metallic bases of +the gold held in solution. + +We will, however, take, to begin with, the generally accepted theory as +to the occurrence of alluvial gold. First, let it be said, that certain +alluvial gold is unquestionably derived from the denudation of quartz +lodes. Such is the gold dust found in many Asiatic and African rivers, +in the great placer mines of California, as also the gold dust gained +from the beach sand on the west coast of New Zealand, or in the enormous +alluvial drifts of the Shoalhaven Valley, New South Wales. Of the +first, many fabulous tales are told to account for its being found in +particular spots each summer after the winter floods, and miraculous +agency was asserted, while the early beachcombers of the Hokitika +district found an equally ridiculous derivation for their gold, which +was always more plentiful after heavy weather. They imagined that the +breakers were disintegrating some abnormally rich auriferous reefs out +at sea, and that the resultant gold was washed up on the beach. + +The facts are simply, with regard to the rivers, that the winter floods +break down the drifts in the banks and agitate the auriferous detritus, +thus acting as natural sluices, and cause the metal to accumulate +in favourable spots; whilst on the New Zealand coast the heavy seas +breaking on the shingly beach, carry off the lighter particles, leaving +behind the gold, which is so much heavier. These beaches are composed, +as also are the "terraces" behind, of enormous glacial and fluvial +deposits, all containing more or less gold, and extend inland to the +foot of the mountains. + +It is almost certain that the usually fine gold got by hydraulicing in +Californian canyons, in the gullies of the New Zealand Alps, and the +great New South Wales drifts, is largely the result of the attrition of +the boulders and gravel of moraines, which has thus freed, to a certain +extent, the auriferous particles. But when we find large nuggety masses +of high carat gold in the beds of dead rivers, another origin has to be +sought. + +As previously stated, there is fair reason to assume that at least +three salts of gold have existed, and, possibly, may still be found in +Nature--silicate, sulphide, and chloride. All of these are soluble and +in the presence of certain reagents, also existing naturally, can be +deposited in metallic form. Therefore, if, as is contended, reef +gold was formed with the reefs from solutions in mineral waters, by +inferential reasoning it can be shown that much of our alluvial gold was +similarly derived. + +The commonly accepted theory, however, is that the alluvial matter of +our drifts has been ground out of the solid siliceous lodes by glacial +and fluvial action, and that the auriferous leads have been formed by +the natural sluicing operations of former streams. To this, however, +there are several insuperable objections. + +First, how comes it that alluvial gold is usually superior in purity to +the "reef" gold immediately adjacent? Second, why is it that masses of +gold, such as the huge nuggets found in Victoria and New South Wales, +have never been discovered in lodes? Third, how is it that these heavy +masses which, from their specific gravity, should be found only at the +very bottom of the drifts, if placed by water action, are sometimes +found in all positions from the surface to the bottom of the "wash"? +And, lastly, why is it that when an alluvial lead is traced up to, or +down from, an auriferous reef, that the light, angular gold lies close +to the roof, while the heavy masses are often placed much farther away? +Any one who has worked a ground sluice knows how extremely difficult it +is with a strong head of water to shift from its position an ounce +of solid gold. What, then, would be the force required to remove the +Welcome Nugget? Under certain circumstances, Niagara would not be equal +to the task. + +The generally smooth appearance of alleged alluvial gold is adduced +as an argument in favour of its having been carried by water from its +original place of deposit, and thus in transit become waterworn; while +some go so far as to say that it was shot out of the reefs in a molten +state. The latter idea has been already disposed of, but if not, it may +be dismissed with the statement that the heat which would melt silica +in the masses met with in lodes would sublimate any gold contained, and +dissipate it, not in nuggets but in fumes. With regard to the assumed +waterworn appearance of alluvial gold, I have examined with the +microscope the smooth surface of more than one apparently waterworn +nugget, and found that it was not scratched and abraded, as would have +been the case had it been really waterworn, but that it presented the +same appearance, though infinitely finer in grain, as the surface of a +piece of metal fresh from the electrical plating-bath. + +Mr. Daintree, of the Victorian Geological Survey, many years ago +discovered accidentally that gold chloride would deposit its metal on +a metallic base in the presence of any organic substance. Mr. Daintree +found that a piece of undissolved gold in a bottle containing chloride +of gold in solution had, owing to a portion of the cork having fallen +into the liquid, grown or accretionised so much that it could not be +extracted through the neck. This lead Mr. Charles Wilkinson, who +has contributed much to our scientific knowledge of metallurgy, to +experiment further in the same direction. He says: "Using the most +convenient salt of gold, the terchloride, and employing wood as the +decomposing agent, in order to imitate as closely as possible the +organic matter supposed to decompose the solution circulating through +the drifts, I first immersed a piece of cubic iron pyrites taken from +the coal formation of Cape Otway, far distant from any of our gold +rocks, and therefore less likely to contain gold than other pyrites. The +specimen (No. 1) was kept in dilute solution for about three weeks, and +is completely covered with a bright film of gold. I afterwards filed off +the gold from one side of a cube crystal to show the pyrites itself and +the thickness of the surrounding coating, which is thicker than ordinary +notepaper. If the conditions had continued favourable for a very +lengthened period, this specimen would doubtless have formed the nucleus +of a large nugget. Iron, copper, and arsenical pyrites, antimony, +galena, molybdenite, zinc blende, and wolfram were treated in the above +manner with similar results. In the above experiments a small chip of +wood was employed as the decomposing agent. In one instance I used a +piece of leather. All through the wood and leather gold was disseminated +in fine particles, and when cut through the characteristic metallic +lustre was brightly reflected. The first six of these sulphides were +also operated upon simply in the solution without organic matter; but +they remained unaltered." + +Wilkinson found that when the solution of gold chloride was as strong +as, say, four grains to the ounce of water, that the pyrites or other +base began to decompose, and the iron sulphide changed to yellow oxide, +the "gossan" of our lodes, and that though the gold was deposited, +this occurred in an irregular way, and it was coated with a dark brown +powdery film something like the "black gold," often found in drifts +containing much ferruginous matter. Such were the curious Victorian +nuggets Spondulix and Lothair. + +Professor Newbery also made a number of similar experiments, and arrived +at like results. He states as follows: "I placed a cube of galena in +a solution of chloride of gold, with free access of air, and put in +organic matter; gold was deposited as usual, in a bright metallic film, +apparently completely coating the cube. After a few months the film +burst along the edges of the cube, and remained in that state with +the cracks open without any further alteration in size or form being +apparent. Upon removing it a few days ago and breaking it open, I found +that a large portion of the galena had been decomposed, forming chloride +and sulphate of lead and free sulphur, which were mixed together, +encasing a small nucleus of undecomposed sulphate of lead. The formation +of these salts had exerted sufficient force to burst open the gold +coating, which upon the outside had the mammillary form noticed by +Wilkinson, while the inside was rough and irregular with crystals +forcing their way into the lead salts. Had this action continued +undisturbed, the result would have been a nugget with a nucleus of +lead salts, or if there had been a current to remove the results of +decomposition, a nugget without a nucleus of foreign matter." + +But Newbery also made another discovery which still further establishes +the probability of the accretionary growth of gold in drifts. In the +first experiments both investigators used organic substances as the +reagent to cause the deposit of gold on its base, and in each case these +substances whether woodchips, leather, or even dead flies, were found +to be so absolutely impregnated with gold as to leave a golden skeleton +when afterwards burned. Timber found in the Ballarat deep leads has been +proved to be similarly impregnated. + +Newbery found that gold could also be deposited on sulphurets without +any other reagent. He says: "In our mineral sulphurets, however, we +have agents which are not only capable of reducing gold and silver from +solution, but besides are capable of locating them when so reduced in +coherent and bulky masses. Thus the aggregation of the nuggety forms of +gold from solution becomes a still more simple matter, only one +reagent being necessary, so that there is a greater probability of such +depositions obtaining than were a double process necessary. Knowing the +action of sulphides, the manner or the mode of formation of a portion at +least of these nuggets seems apparent. Conceive a stream or river fed +by springs rising in a country intersected by auriferous reefs, and +consequently in this case carrying gold in solution; the drift of such +a country must be to a greater or lesser extent pyritous, so that the +_debris_ forming the beds of these streams or rivers will certainly +contain nodules of such matters disseminated or even stopping them in +actual contact with the flow of water. It follows, then, from what has +been previously affirmed, that there will be a reduction of gold by +these nodules, and that the metal thus reduced will be firmly attached +to them, at first in minute spangles isolated from each other, but +afterwards accumulating and connecting in a gradual manner at that point +of the pyritous mass most subject to the current until a continuous film +of some size appears. This being formed the pyrites and gold are to a +certain extent polarised, the film or irregular but connected mass of +gold forming the negative, and the pyrites the positive end of a voltaic +pair; and so according as the polarisation is advanced to completion +the further deposition of gold is changed in its manner from an +indiscriminate to an orderly and selective deposition concentrated +upon the negative or gold plate. The deposition of gold being thus +controlled, its loss by dispersion or from the crumbling away of the +sustaining pyrites is nearly or quite prevented, a conservative effect +which we could scarcely expect to obtain if organic matter were the +reducing agent. Meanwhile there is a gradual wasting away of the pyrites +or positive pole, its sulphur being oxidised to sulphuric acid and its +iron to sesquioxide of iron, or hematite, a substance very generally +associated with gold nuggets. According to the original size of the +pyritous mass, the protection it receives from the action of oxidising +substances other than gold, the strength of the gold solution, length of +exposure to it, the rate of supply and velocity of stream, will be the +size of the gold nugget. As to the size of a pyritous mass necessary to +produce in this manner a large nugget, it is by no means considerable. +A mass of common pyrites (bisulphide of iron) weighing only 12 lbs. +is competent for the construction of the famous 'Welcome Nugget,' an +Australian find having weight equal to 152 lbs. avoirdupois. Such masses +of pyrites are by no means uncommon in our drifts or the beds of our +mountain streams. Thus we find that no straining of the imagination is +required to conceive of this mode of formation for the huge masses of +gold found in Australia in particular, such as the Welcome Nugget, +184 lbs. 9 oz.; the Welcome Stranger, a surface nugget, 190 lbs. after +smelting; the Braidwood specimen nugget, 350 lbs., two-thirds gold; +besides many other large masses of almost virgin gold which have been +obtained from time to time in the alluvial diggings." + +The author has made a number of experiments in the same direction, but +more with the idea of demonstrating how possibly gold may in certain +cases have been deposited in siliceous formations after such formations +had solidified. Some of the results were remarkable and indeed +unexpected. I found that I could produce artificial specimens of +auriferous quartz from stone which had previously contained no gold +whatever, also that it was not absolutely necessary that the stone so +treated should contain any metallic sulphides. + +The following was contributed by the author and is from the +"Transactions" of the Australasian Institute of Mining Engineers for +1893:-- + +"THE DEPOSITION OF GOLD. + +"The question as to how gold was originally deposited in our auriferous +lodes is one to which a large amount of attention has been given, both +by mineralogists and practical miners, and which has been hotly argued +by those who held the igneous theory and those who pronounced for the +aqueous theory. It was held by the former that as gold was not probably +existent in nature in any but its metallic form, therefore it had been +deposited in its siliceous matrix while in a molten state, and many +ingenious arguments were adduced in support of this contention. Of late, +however, most scientific men, and indeed many purely empirical inquirers +(using the word empirical in its strict sense) have come to the +conclusion that though the mode in which they were composed was not +always identical, all lodes, including auriferous formations, were +primarily derived from mineral-impregnated waters which deposited their +contents in fissures caused either by the cooling of the earth's crust +or by volcanic agency. + +"The subject is one which has long had a special attraction for the +writer, who has published several articles thereon, wherein it was +contended that not only was gold deposited in the lodes from aqueous +solution, but that some gold found in form of nuggets had not been +derived from lodes but was nascent in its alluvial bed; and for this +proof was afforded by the fact that certain nuggets have been unearthed +having the shape of an adjacent pebble or angular fragment of stone +indented in them. Moreover, no true nugget of any great size has ever +been found in a lode such as the Welcome, 2159 oz., or the Welcome +Stranger, 2280 oz.; while it was accidentally discovered some years ago +that gold could be induced to deposit itself from its mineral salt to +the metallic state on any suitable base, such as iron sulphide. + +"Following out this fact, I have experimented with various salts of +gold, and have obtained some very remarkable results. I have found it +practicable to produce most natural looking specimens of auriferous +quartz from stone which previously, as proved by assay, contained no +gold whatever. Moreover, the gold, which penetrates the stone in a +thorough manner, assumes some of the more natural forms. It is always +more or less mammillary, but at times, owing to causes which I have not +yet quite satisfied myself upon, is decidedly dendroidal, as may be seen +in one of the specimens which I have submitted to members. Moreover, +I find it possible to moderate the colour and to produce a specimen in +which the gold shall be as ruddy yellow as in the ferro-oxide gangue of +Mount Morgan, or to tone it to the pale primrose hue of the product of +the Croydon mines. + +"I note that the action of the bath in which the stone is treated has a +particularly disintegrating effect on many of the specimens. Some, which +before immersion were of a particularly flinty texture, became in a few +weeks so friable that they could be broken up by the fingers. So far +as my experiments have extended they have proved this, that it was not +essential that the silica and gold should have been deposited at the one +time in auriferous lodes. A non-auriferous siliceous solution may have +filled a fissure, and, after solidifying, some volcanic disturbance may +have forced water impregnated with a gold salt through the interstices +of the lode formation, when, if the conditions were favourable, the gold +would be deposited in metallic forms. I prefer, for reasons which will +probably be understood, not to say exactly by what process my results +are obtained, but submit specimens for examination. + +"(1) Piece of previously non-gold bearing stone. Locality near Adelaide, +now showing gold freely in mammillary and dendroidal form. + +"(2) Stone from New South Wales, showing gold artificially introduced in +interstices and on face. + +"(3) Stone from West Australia, very glassy looking, now thoroughly +impregnated with gold; the mammillary formation being particularly +noticeable. + +"(4) Somewhat laminated quartz from Victoria, containing a little +antimony sulphide. In this specimen the gold not only shows on the +surface but penetrates each of the laminations, as is proved by +breaking. + +"(5) Consists of fragments of crystallised carbonate of lime from +Tarrawingee, in which the gold is deposited in spots, in appearance like +ferrous oxide, until submitted to the magnifying glass. + +"The whole subject is worthy of much more time than I can possibly give +it. The importance lies in this: That having found how the much desired +metal may have been deposited in its matrix, the knowledge should help +to suggest how it may be economically extracted therefrom." + +A very remarkable nugget weighing 16 3/4 oz. was sluiced from near the +surface in one of my own mining properties at Woodside, South Australia, +some years ago, which illustrated the nuclear theory very beautifully. +This nugget is very irregular in shape, fretted and chased as though +with a jeweller's graving tool, showing plainly the shape of the +pyritous crystals on which it was formed while the interstices were +filled with red hematite iron just as found in artificially formed +nuggets on a sulphide of iron base. The author has a nugget from the +same locality weighing about 1 1/2 oz. which exhibits in a marked degree +the same characteristics, as indeed does most of the alluvial gold +found in the Mount Lofty Ranges; also a nugget from near the centre +of Australia weighing four ounces, in which the original crystals of +pyrites are reproduced in gold just as an iron horse-shoe, placed in +a launder through which cupriferously impregnated water flows, will in +time be changed to nearly pure copper and yet retain its shape. + +Now with regard to the four points I have put as to the apparent +anomalies of occurrence of alluvial gold. The reason why alluvial gold +is of finer quality as a rule than reef is probably because while gold +and silver, which have a considerable affinity for each other, were +presumably dissolved from their salts and held in solution in the same +mineral water, they would in many cases not be deposited together, for +the reason that silver is most readily deposited in the presence of +alkalies, which would be found in excess in mineral waters coming direct +from the basic rocks, while gold is induced to precipitate more quickly +in acid solutions, which would be the character of the waters after +they had been exposed to atmospheric action and to contact with organic +matters. + +This, then, may explain not only the comparatively greater purity of the +alluvial gold, but also why big nuggets are found so far from auriferous +reefs, and also why heavy masses of gold have been frequently unearthed +from among the roots even of living trees, but more particularly in +drifts containing organic matter, such as ancient timber. + +All, then, that has been adduced goes to establish the belief that the +birthplace of our gold is in certain of the earlier rocks comprising the +earth's crust, and that its appearance as the metal we value so highly +is the result of electro-chemical action, such as we can demonstrate in +the laboratory. + + + +CHAPTER VI + +GOLD EXTRACTION + +We now come to a highly important part of our subject, the practical +treatment of ores and matrixes for the extraction of the metals +contained. The methods employed are multitudinous, but may be divided +into four classes, namely, washing, amalgamating with mercury, +chlorinating, cyaniding and other leaching processes, and smelting. The +first is used in alluvial gold and tin workings and in preparing some +silver, copper, and other ores for smelting, and consists merely in +separating the heavier metals and minerals from their gangues by their +greater specific gravity in water. The second includes the trituration +of the gangue and the extraction of its gold or silver by means of +mercury. Chlorinating and leaching generally is a process whereby +metals are first changed by chemical action into their mineral salts, +as chloride of gold, nitrate of silver, sulphate of copper, and being +dissolved in water are afterwards redeposited in the metallic form by +means of well-known re-agents. + +In really successful mining it is in the last degree important that the +mode of extraction of metals in the most scientific manner should be +thoroughly understood, but as a general rule the science of metallurgy +is but very superficially grasped even by those whose special business +it is to treat ore bodies in order to extract their metalliferous +contents, and whether in quartz crushing mill, lixiviating, or smelting +works there is much left to be desired in the method of treating our +ores. + +My attention was recently attracted to an article written by Mr. F. A. +H. Rauft, M.E., from which I make the following extract: + +He says, speaking of the German treatment of ores and the mode of +procedure in Australia, "It is high time that Government stepped in and +endeavoured by prompt and decisive action to bring the mining industry +upon a sound and legitimate basis. Though our ranges abound in all +kinds of minerals that might give employment to hundreds of thousands of +people, mining is carried on in a desultory, haphazard fashion. There is +no system, and the treatment of ores is of necessity handed over to the +tender mercies of men who have not even an idea of what an intricate +science metallurgy has become in older countries. During many years of +practical experience I have never known a single instance where a lode, +on being worked, gave a return according to assay, and I have never +known any mine where some of the precious metals could not be found in +the tailings or slag. The Germans employ hundreds of men in working for +zinc which produces some two or three per cent to the ton; here the same +percentage of tin could hardly be made payable, and this, mark you, +is owing not to cheaper labour alone, but chiefly to the labour-saving +appliances and the results of the researches of such gigantic intellects +as Professor Kerl and many others, of whom we in this country never even +hear. Go into any of the great mining works of central Germany, and you +may see acres covered by machinery ingeniously constructed to clean, +break, and sort, and ultimately deliver the ores into trucks or direct +into the furnace, and the whole under the supervision of a youngster or +two. When a parcel of ore arrives at any of the works, say Freiberg or +Clausthal, it is carefully assayed by three or four different persons +and then handed over to practical experts, who are expected to produce +the full amount of previous metal according to assay; and if by any +chance they do not, a fixed percentage of the loss is deducted from +their salary; or, if the result is in excess of this assay which is more +frequently the case, a small bonus is added to their pay. Compare +this system with our own wasteful, reckless method of dealing with our +precious metals, and we may hide our heads in very shame." + +All really practical men will, I think, endorse Mr. Rauft's opinion. +Well organised and conducted schools of mines will gradually ameliorate +this unsatisfactory state of things, and I hope before long that we +shall have none but qualified certificated men in our mines. In the +meantime a few practical hints, particularly on that very difficult +branch of the subject, the saving of gold, will, it is hoped, be found +of service. + +The extraction of gold from the soil is an industry so old that its +first introduction is lost in the mist of ages. As before stated, gold +is one of the most widely disseminated of the metals, and man, so soon +as he had risen from the lowest forms of savagery, began to be attracted +by the kingly metal, which he found to be easily fashioned into articles +of ornament and use, and to be practically non-corrodable. + +What we now term the dish or pan, then, doubtless generally a wooden +bowl, was the appliance first used; but they had also an arrangement, +somewhat like our modern blanket tables, over which the auriferous +sand was passed by means of a stream of water. The sands of some of +the rivers from which portions of the gold supply of the old world was +derived are still washed over year after year in exactly the same manner +as was employed, probably, thousands of years ago, the labour, very +arduous, being often carried on by women, who, standing knee deep in +water, pan off the sand in wooden bowls much as the digger in modern +alluvial fields does with his tin dish. The resulting gold often +consists of but a grain or two of fine dust-gold, which is carefully +collected in quills, and so exported or traded for goods. + +The digger of to-day having discovered payable alluvial dirt at such a +depth as to permit of its being profitably worked by small parties of +men with limited or no capital, procures first a half hogshead for a +puddling tub, a "cradle," or "long tom," and tin dish. The "wash dirt," +as the auriferous drift is usually termed, contains a considerable +admixture of clay of a more or less tenacious character, and the bulk of +this has to be puddled and so disintegrated before the actual separation +of the gold is attempted in the cradle or dish. This is done in the +tub by constantly stirring with a shovel, and changing the water as it +becomes charged with the floating argillaceous, or clayey, particles. +The gravel is then placed in the hopper of the cradle which separates +the larger stones and pebbles, the remainder passing down over inclined +ledges as the cradle is slowly rocked and supplied with water. At +the bottom of each ledge is a riffle to arrest the particles of gold. +Sometimes, when the gold is very fine, amalgamated copper plates are +introduced and the lower ledges are covered with green baize to act as +blanket tables and catch gold which might otherwise be lost. + +A long tom is a trough some 12 feet in length by 20 inches in width at +the upper end, widening to 30 inches at the lower end; it is about 9 +inches deep and has a fall of 1 inch to a foot. An iron screen is placed +at the lower end where large stones are caught, and below this screen +is the riffle box, 12 feet long, 3 feet wide, and having the same +inclination as the upper trough. It is fitted with several riffles in +which mercury is sometimes placed. + +Much more work can be done with this appliance than with the cradle, +which it superseded. Of course, the gold must be coarse and water +plentiful. + +When, however, the claim is paying, and the diggings show signs of some +permanency, a puddling machine is constructed. This is described in the +chapter called "Rules of Thumb." + +Hydraulicing and ground sluicing is a very cheap and effective method +of treating large quantities of auriferous drift, and, given favourable +circumstances, such as a plentiful supply of water with good fall and +extensive loose auriferous deposits, a very few grains to the ton or +load can be made to give payable returns. The water is conveyed in +flumes, or pipes to a point near where it is required, thence in wrought +iron pipes gradually reduced in size and ending in a great nozzle +somewhat like that of a fireman's hose. The "Monitor," as it is +sometimes called, is generally fixed on a movable stand, so arranged +that the strong jet of water can be directed to any point by a simple +adjustment. A "face" is formed in the drift, and the water played +against the lower portion of the ledge, which is quickly undermined, and +falls only to be washed away in the stream of water, which is conducted +through sluices with riffles, and sometimes over considerable lengths +of amalgamated copper plates. This class of mining has been most +extensively carried out in California and New Zealand, and some +districts of Victoria, but the truly enormous drifts of the Shoalhaven +district in New South Wales must in the near future add largely to the +world's gold supply. These drifts which are auriferous from grass roots +to bed rock extend for nearly fifty miles, and are in places over 200 +feet deep. Want of capital and want of knowledge has hitherto prevented +their being profitably worked on a large scale. + +The extraction of reef gold from its matrix is a much more complicated +process, and the problem how most effectively to obtain that great +desideratum--a complete separating and saving operation--is one which +taxes the skill and evokes the ingenuity of scientific men all over the +world. The difficulty is that as scarcely any two gangues, or matrixes, +are exactly alike, the treatment which is found most effective on +one mine will often not answer in another. Much also depends on the +proportion of gold to the ton of rock under treatment, as the most +scientific and perfect processes of lixiviation hitherto adopted will +not pay, even when all other conditions are favourable, if the amount of +gold is much under half an ounce to the ton and even then will leave +but a very small profit. If, however, the gold is "free," and the lode +large, a very few pennyweights (or "dollars," as the Americans say) to +the ton will pay handsomely. The mode of extraction longest in vogue, +and after all the cheapest and most effective, for free milling ores +where the gold is not too fine, is amalgamation with mercury, which +metal has a strong affinity for gold, silver, and copper. + +As to crushing appliances, I shall not say much. "Their name is legion +for they are many," and the same may be said of concentrators. It may +be old-fashioned, but I admit my predilection is still in favour of +the stamper-battery, for the reason that though it may be slower in +proportion to the power employed, it is simple and not liable to get out +of order, a great advantage when one has so often to depend on men who +bring to their work a supply principally of main strength and stupidity. +For the same reason I prefer the old draw and lift, and plunger pumps to +newer but more complicated water-lifters. + +On both these points, however, I am constrained to admit that my opinion +has recently been somewhat shaken. + +I have lately seen two appliances which appear to mark a new era in the +scientific progress of mining. One is the "Griffin Mill," the other the +"Lemichel Siphon Elevateur." + +The first is in some respects on the principle of the Huntingdon Mill. +The latter, if the inventor may be believed and the results seem to +show he can be, will be a wonderful factor in developing not only mining +properties where a preponderance of water is the trouble, but also +in providing an automatic, and therefore extremely cheap, mode of +water-raising and supply, which in simplicity is thus far unexampled. +Atmospheric pressure alone is relied on. The well-known process of the +syphon is the basis, but with this essential difference, that a +large proportion of the water drawn up to the apex of the syphon is +super-elevated to heights regulated by the fall obtained in the outlet +leg. This elevation can be repeated almost indefinitely by returning the +waste water to the reservoirs. + +The Lemichel Syphon is a wonderful, yet most simple application of +natural force. The inlet leg of the syphon is larger in diameter than +the outlet leg, and is provided at the bottom with a valve or "clack." +The outlet leg has a tap at its base. At the apex are two chambers, with +an intermediary valve, regulated by a counterpoise weighted lever. The +first chamber has also a vertical valve and pipe. + +When the tap of the outlet leg is turned, the water flows as in an +ordinary syphon, but owing to the rapid automatic opening and shutting +of the valve in the first chamber about 45 per cent of the water is +diverted, and may be raised to a height of many feet above the top of +the syphon. + +It need not be impressed on practical men that if this invention will +perform anything like what is claimed for it, its value can hardly be +calculated. After a careful inspection of the appliance in operation, I +believe it will do all that is stated. + +Another invention is combined with this which, by a very small +expenditure of fuel, will enable the first point of atmospheric +pressure to be attained. In this way the unwatering of mines may be very +inexpensively effected, or water for irrigation purposes may be raised +from an almost level stream. + +The Griffin Mill is a centrifugal motion crusher with one roller only, +which, by an ingenious application of motive force, revolves in an +opposite direction to its initial momentum, and which evolves a force of +6000 lb. against the tire, which is only 30 inches in diameter. For hard +quartz the size should be increased by at least 6 inches. It is claimed +for this mill that it will pulverise to a gauge of 900 holes to the +square inch from 1 1/2 to 2 1/2 tons per hour, or, say roughly, 150 tons +per week. + +The Huntingdon mill is a good crusher and amalgamator where the material +to be operated on is comparatively soft, but does not do such good work +when the stone is of a hard flinty nature. + +A No. 4 Dodge stone-breaker working about 8 hours will keep a five-foot +Huntingdon mill going 24 hours, and an automatic feeder is essential. +For that matter both are almost essential for an ordinary stamper +battery, and will certainly increase the crushing capacity and do better +work from the greater regularity of the feed. + +A 10 h.-p. (nominal) engine of good type is sufficient for Huntingdon +mill, rock breaker, self-feeder and steam pump. A five-foot mill under +favourable circumstances will crush about as much as eight head of +medium weight stamps. + +The Grusonwek Ball Mills, made by Krupp of Germany, also that made by +the Austral Otis Company, Melbourne, are fast and excellent crushing +triturating appliances for either wet or dry working, but are specially +suited only for ores when the gold is fine and evenly distributed in +the stone. The trituration is effected by revolving the stone in a large +cylinder together with a number of steel balls of various sizes, the +attrition of which with the rock quickly grinds it to powder of any +required degree of fineness. + +More mines have been ruined by bad mill management probably than by bad +mining, though every experienced man must have seen in his time many +most flagrant instances of bungling in the latter respect. Shafts are +often sunk on the wrong side of the lode or too near or too far away +therefrom, while instances have not been wanting where the (mis) manager +has, after sinking his shaft, driven in the opposite direction to that +where the lode should be found. + +A common error is that of erecting machinery before there is sufficient +ore in sight to make it certain that enough can be provided to keep the +plant going. In mines at a distance from the centre of direction it is +almost impossible to check mistakes of this description, caused by the +ignorance or over sanguineness of the mine superintendent, and they are +often as disastrous as they are indefensible. Another fertile source of +failure is the craze for experimenting with untried inventions, alleged +to be improvements on well-known methods. + +A rule in the most scientific of card games, whist, is "when in doubt +lead trumps." It might be paraphrased for mining thus: "When in doubt +about machinery use that which has been proved." Let some one else do +the experimenting. + +The success of a quartz mine depends as much on favourable working +conditions as on its richness in gold. Thus it may be that a mine +carrying 5 or 6 oz. of gold to the ton but badly circumstanced as to +distance, mountainous roads, lack of wood and water, in some cases a +plethora of the latter, or irregularly faulted country, may be less +profitable than another showing only 5 or 6 dwt., but favourably +situated. + +It is usually desirable to choose for the battery site, when possible, +the slope of a hill which consists of rock that will give a good +foundation for your battery. + +The economical working depends greatly on the situation, which is +generally fixed more or less, in the proximity of the water. The +advantages of having ample water for battery purposes, or of using +water as a motive power, are so great that it is very often desirable +to construct a tramway of considerable length, when, by so doing, that +power can be utilised; hence most quartz mills are placed near streams, +or in valleys where catchment dams can be effectively constructed, +except, of course, in districts where much water has to be pumped from +the mine. + +If water-power can be used, the water-motor will necessarily be placed +as low as possible, in order to obtain the fullest available power. One +point is essential. Special care must be taken to keep the appliances +above the flood-level. If the water in the stream is not sufficient to +carry off the tailings, the battery should be placed at such a height +as to leave sufficient slope for tailings' dumps. This is more important +when treating ore of such value that the tailings are worth saving for +secondary treatment. In this case provision should be made for tailings, +dams, or slime pits. + +Whether the battery is worked by water, steam, or gas power, an ample +supply of water is absolutely necessary, at least until some thoroughly +effective mode of dry treatment is established. If it can be possibly +arranged the water should be brought in by gravitation, and first cost +is often least cost; but where this is impossible, pumps of sufficient +capacity, not only to provide the absolute quantity used, but to meet +any emergency, should be erected. + +The purer the water the better it will be for amalgamating purposes, and +in cold climates it is desirable to make provision for heating the water +supplied to the battery. This can be done by means of steam from the +boiler led through the feed tanks; but where the boiler power is not +more than required, waste steam from the engine may be employed, but +care must be taken that no greasy matter comes in contact with the +plates. The exhaust steam from the engine may be utilised by carrying it +through tubes fitted in an ordinary 400 gallon tank. + +Reducing appliances have often to be placed in districts where the water +supply is insufficient for the battery. When this is so every available +means must be adopted for saving the precious liquid, such as condensing +the exhaust steam from the engine. This may be done by conducting it +through a considerable length of ordinary zinc piping, such as is used +for carrying the water from house roofs. Also tailings pits should be +made, in which the tailings and slimes are allowed to settle, and the +cleared water is pumped back to be again used. These pits should, where +practicable, be cemented. It is usual, also, to have one or two tailings +dams at different levels; the tailings are run into the upper dam, and +are allowed to settle; the slimes overflow from it into the lower dam, +and are there deposited, while the cleared water is pumped back to the +battery. Arrangements are made by which all these reservoirs can be +sluiced out when they are filled with accumulated tailings. It is well +not to leave the sluicing for too long a period, as when the slimes and +tailings are set hard they are difficult to remove. + +Where a permanent reducing plant is to be erected, whatever form of +mill may be adopted, it is better for many reasons to use automatic +ore feeders. Of these the best two I have met are the "Tulloch" and +"Challenge" either of which can be adapted to any mill and both do good +work. + +By their use the reducing capacity of the mill is increased, and the +feeding being regular the wear and tear is decreased, while by the +regulated feeding of the "pulp" in the battery box or mortar can be +maintained at any degree of consistency which may be found desirable, +and thus the process of amalgamation will be greatly facilitated. The +only objection which can be urged against the automatic feeder is that +the steel points of picks, gads, drills, and other tools may be allowed +to pass into the mortar or mill, and thus cause considerable wear +and tear. This, I think, can be avoided by the adoption of the magnet +device, described in "Rules of Thumb." + +There are many mines where 3 to 4 dwt. of gold cover all the cost, the +excess being clear profit. In fact there are mines which with a yield +of 1 1/2 to 2 dwt. a ton, and crushing with water power, have actually +yielded large profits. On the other hand, mines which have given +extraordinary trial crushings have not paid working expenses. Everything +depends on favourable local conditions and proper management. + +Having decided what class of crushing machinery you will adopt, the +first point is to fix on the best possible site for its erection. This +requires much judgment, as success or failure may largely depend on +the position of your machinery. One good rule is to get your crusher as +reasonably high as possible, as it is cheaper to pump your feed water +a few feet higher so as to get a good clear run for your tailings, and +also to give you room to erect secondary treatment appliances, such +as concentrators and amalgamators below your copper plates and blanket +strakes. + +Next, and this is most important, see that your foundations are solid +and strong. A very large number of the failures of quartz milling plants +is due to neglect of this rule. + +I once knew a genius who erected a 10-Lead mill in a new district, and +who adopted the novel idea of placing a "bed log" laterally beneath +his stampers. The log was laid in a little cement bed which, when the +battery started, was not quite dry. The effect was comical to every one +but the unfortunate owners. It was certainly the liveliest, but at the +same time one of the most ineffective batteries I have seen. + +In a stamp mill the foundations are usually made of hard wood logs about +5 to 6 feet long, set on end, the bottom end resting on rock and set +round with cement concrete. These are bolted together, and the "box" or +mortar is bolted to them. The horizontal logs to carry the "horses" or +supports for the battery frame should also be of good size, and solidly +and securely bolted. The same applies to your engine-bed, but whether it +be of timber, or mason work, above all things provide that the whole of +your work is set out square and true to save after-wear and friction. + +Considerable difference of opinion exists as to the most effective +weight for stamps. My experience has been that this largely depends on +the nature of your rock, as does also the height for the drop. I have +usually found that with medium stamps, say 7 to 7 1/2 cwt. with fair +drop and lively action, about 80 falls per minute, the best results were +obtained, but the tendency of modern mill men is towards the heavier +stamps, 9 cwt. and even heavier. + +To find the horse-power required to drive a battery, multiply the weight +of one stamp by the number of stamps in the battery; the height of lift +in feet by the number of lifts per minute; add one-third of the product +for friction, and the result will be the number of feet-lbs. per minute; +divide this by 33,000 which is the number of feet-lbs. per minute equal +to 1 h.-p. and the result will be the h.-p. required. Thus if a stamp +weighs 800 lb. and you have five in the box, and each stamp has a lift +of 9 in. = 0.75 ft. and strikes 80 blows per minute, then 800 x 5 x 0.75 +x 80 = 240,000; one-third of 240,000 = 80,000 which added to 240,000 += 320,000; and 320,000 divided by 33,000 = 9.7 h.-p. or 1.9 h.-p. each +stamp. + +The total weight of a battery, including stamper box, stampers, etc., +may be roughly estimated at about 1 ton per stamp. Medium weight +stampers, including shank cam, disc, head, and shoe, weigh from 600 to +700 lb., and need about 3/4 h.-p. to work them. + +The quantity of water required for the effective treatment of +gold-bearing rock in a stamper battery varies according to the +composition of the material to be operated upon, but generally it is +more than the inexperienced believe. For instance, "mullocky" lode +stuff, containing much clayey matter or material carrying a large +percentage of heavy metal, such as titanic iron or metallic sulphides, +will need a larger quantity of water per stamp than clean quartz. A fair +average quantity would be 750 to 1000 gallons per hour for each box of +five stamps. In general practice I have seldom found 1000 gallons per +hour more than sufficient. + +As to the most effective mesh for the screen or grating no definite +rule can be given, as that depends so largely on the size of the gold +particles contained in the gangue. The finer the particles the closer +must be the mesh, and nothing but careful experiment will enable the +battery manager to decide this most important point. The American +slotted screens are best; they wear better than the punched gratings and +can be used of finer gauge. Woven steel wire gauze is employed with good +effect in some mills where especially fine trituration is required. This +class of screen requires special care as it is somewhat fragile, but +with intelligent treatment does good work. + +The fall or inclination of the tables, both copper and blanket strakes, +is also regulated by the class of ore. If it should be heavy then the +fall must be steeper. A fair average drop is 3/4 inch to the foot. Be +careful that your copper tables are thoroughly water-tight, for remember +you are dealing with a very volatile metal, quicksilver; and where water +will percolate mercury will penetrate. + +The blanket tables are simply a continuation of the mercury tables, but +covered with strips of coarse blanket, green baize, or other flocculent +material, intended to arrest the heavier metallic particles which, owing +to their refractory nature, have not been amalgamated. + +The blanket table is, however, a very unsatisfactory concentrator +at best, and is giving place to mechanical concentrators of various +descriptions. + +An ancient Egyptian gold washing table was used by the Egyptians in +treating the gold ores of Lower Egypt. The ore was first ground, it is +likely by means of some description of stone arrasts and then passed +over the sloping table with water, the gold being retained in the +riffles. In these the material would probably be mechanically agitated. +Although for its era ingenious it will be plain to practical men that if +the gold were fine the process would be very ineffective. Possibly, but +of this I have no evidence, mercury was used to retain the gold on the +riffles, as previously stated. This method of saving the precious metal +was known to the ancients. + +At a mine of which I was managing director the lode was almost entirely +composed of sulphide of iron, carbonate of lime or calcspar, with a +little silica. In this case it has been found best to crush without +mercury, then run the pulp into pans, where it is concentrated. The +concentrates are calcined in a common reverberatory furnace, and +afterwards amalgamated with mercury in a special pan, the results as to +the proportion of gold extracted being very satisfactory; but it does +not therefore follow that this process would be the most suitable in +another mine where the lode stuff, though in some respects similar, yet +had points of difference. + +I was lately consulted with respect to the treatment of a pyritic ore +in a very promising mine, but could not recommend the above treatment, +because though the pyrites in the gangue was similar, the bulk of the +lode consisted of silica, consequently there would be a great waste of +power in triturating the whole of the stuff to what, with regard to much +of it, would be an unnecessary degree of fineness. I am of opinion +that in cases such as this, where it is not intended to adopt the +chlorination or cyanogen process, it will be found most economical to +crush to a coarse gauge, concentrate, calcine the concentrates, and +finally amalgamate in some suitable amalgamator. + +Probably for this mode of treatment Krom rolls would be found more +effective reducing agents than stampers, as with them the bulk of the +ore can be broken to any required gauge and there would consequently be +less loss in "slimes." + +The great art in effective battery work is to crush your stuff to +the required fineness only, and then to provide that each particle is +brought into contact with the mercury either in box, trough, plate, or +pan. To do this the flow of water must be carefully regulated; neither +so much must be used as to carry the stuff off too quickly nor so little +as to cause the troughs and plates to choke. In cold weather the water +may be warmed by passing the feed-pipe through a tank into which the +steam from the engine exhausts, and this will be found to keep the +mercury bright and lively. But be careful no engine oil or grease +mingles with the water, as grease on the copper tables will absolutely +prevent amalgamation. + +The first point, then, is to crush the gangue effectively, the degree of +fineness being regulated by the fineness of the gold itself. This being +done, then comes the question of saving the gold. If the quartz be +clean, and the gold unmixed with base metal, the difficulty is small. +All that is required is to ensure that each particle of the Royal metal +shall be brought into contact with the mercury. The main object is to +arrest the gold at the earliest possible stage; therefore, if you are +treating clean stone containing free gold, either coarse or fine, +I advise the use of mercury in the boxes, for the reason that a +considerable proportion of the gold will be caught thereby, and settling +to the bottom, or adhering to amalgamated plates in the boxes, where +such are used, will not be afterwards affected by the crushing action, +which might otherwise break up, or "flour," the mercury. On the whole, I +rather favour the use of mercury in the box at any time, unless the ore +is very refractory--that is, contains too great a proportion of base +metals, particularly sulphides of iron, arsenic, etc., when the result +will not be satisfactory, but may entail great loss by the escape of +floured mercury carrying with it particles of gold. Here only educated +intelligence, with experience, will assist the battery manager to adopt +the right system. + +The crushed stuff--generally termed the "pulp"--passes from the boxes +through the "screens" or "gratings," and so on to the "tables"--i.e., +sheets of copper amalgamated on the upper surface with mercury, and +sometimes electroplated with silver and afterwards treated with mercury. +Unless the quartz is very clean, and, consequently light, I am opposed +to the form of stamper box with mercury troughs cast in the "lip," nor +do I think that a trough under the lip is a good arrangement, as it +usually gets so choked and covered with the heavy clinging base metals +as to make it almost impossible for the gold to come in contact with the +mercury. It will be found better where the gold is fine, or the gangue +contains much base metal, to run the pulp from the lip of the battery +into a "distributor." + +The distributor is a wooden box the full width of the "mortar," having +a perforated iron bottom set some three to four inches above the first +copper plate, which should come up under the lip. The effect of this +arrangement is that the pulp is dashed on the plate by the falling +water, and the gold at once coming in contact with the mercury begins +to accumulate and attract that which follows, till the amalgam becomes +piled in little crater-shaped mounds, and thus 75 per cent of the gold +is saved on the top plate. + +I have tried a further adaptation of this process when treating ores +containing a large percentage of iron oxide, where the bulk of the gold +is impalpably fine, and contained in the "gossan." At the end of the +blanket table, or at any point where the crushed stuff last passes +before going to the "tailings heap," or "sludge pit," a "saver" is +placed. The saver is a strong box about 15 in. square by 3 ft. high, +one side of which is removable, but must fit tight. Nine slots are cut +inside at 4 in. apart, and into these are fitted nine square perforated +copper plates, having about eighty to a hundred 1/4 in. holes in each; +the perforations should not come opposite each other. These plates are +to be amalgamated on both sides with mercury, in which a very little +sodium has been placed (if acid ores are being treated, zinc should be +employed in place of sodium, and to prevent the plates becoming bare, if +the stuff is very poor, thick zinc amalgam may be used with good effect; +but in that case discontinue the sodium, and occasionally, if required, +say once or twice in the day, mix an ounce of sulphuric acid in a +quart of water and slowly pour it into the launder above the saver). +Underneath the "saver" you require a few riffles, or troughs, to catch +any waste mercury, but if not overfed there should be no waste. This +simple appliance, which is automatic and requires little attention, will +sometimes arrest a considerable quantity of gold. + +We now come to the subsidiary processes of battery work, the "cleaning" +of plates, and "scaling" same when it is desired to get all the gold +off them, the cleaning and retorting of amalgam, and of the mercury, +smelting gold, etc. + +Plates should be tenderly treated, kept as smooth as possible, and when +cleaning up after crushing, in your own battery, the amalgam--except, +say, at half-yearly intervals--should be removed with a rubber only; the +rubber is simply a square of black indiarubber or soft pine wood. + +When crushing rich ore, and you want to get nearly all the gold off your +plates, the scraper may be resorted to. This is usually made by the mine +blacksmith from an old flat file which is cut in half, the top turned +over, beaten out to a sharp blade, and kept sharp by touching it up on +the grinding-stone. This, if carefully used, will remove the bulk of the +amalgam without injury to the plate. + +Various methods of "scaling" plates will be found among "Rules of +Thumb." + +Where base metals are present in the lode stuff frequent retortings of +the mercury, say not less than once a month, will be found to have a +good effect in keeping it pure and active. For this purpose, and +in order to prevent stoppage of the machinery, a double quantity is +necessary, so that half may be used alternately. Less care is required +in retorting the mercury than in treating the amalgam, as the object +in the one case is more to cleanse the metal of impurities than to save +gold, which will for the most part have been extracted by squeezing +through the chamois leather or calico. A good strong heat may therefore +at once be applied to the retort and continued, the effect being to +oxidise the arsenic, antimony, lead, etc., which, in the form of oxides, +will not again amalgamate with the mercury, but will either lie on +its surface under the water, into which the nozzle of the retort is +inserted, or will float away on the surface of the water. I have also +found that covering the top of the mercury with a few inches of broken +charcoal when retorting has an excellent purifying effect. + +In retorting amalgam, much care and attention is required. + +First, never fill the retort too full, give plenty of room for +expansion; for, when the heat is applied, the amalgam will rise like +dough in an oven, and may be forced into the discharge pipe, the +consequence being a loss of amalgam or the possible bursting of the +retort. Next, be careful in applying the heat, which should be done +gradually, commencing at the top. This is essential to prevent waste and +to turn out a good-looking cake of gold, which all battery managers like +to do, even if they purpose smelting into bars. + +Sometimes special difficulties crop up in the process of separating the +gold from the amalgam. At the first "cleaning up" on the Frasers Mine at +Southern Cross, West Australia, great consternation was excited by the +appearance of the retorted gold, which, as an old miner graphically +put it, was "as black as the hind leg of a crow," and utterly unfit for +smelting, owing to the presence of base metals. Some time after this I +was largely interested in the Blackborne mine in the same district when +a similar trouble arose. This I succeeded in surmounting, but a still +more serious one was too much for me--i.e., the absence of payable +gold in the stone. I give here an extract from the _Australian Mining +Standard_, of December 9th, 1893, with reference to the mode of cleaning +the amalgam which I adopted. + +NEW METHOD OF SEPARATING GOLD FROM IMPURE AMALGAM. + +I had submitted to me lately a sample of amalgam from a mine in West +Australia which amalgam had proved a complete puzzle to the manager +and amalgamator. The Mint returns showed a very large proportion +of impurity, even in the smelted gold. When retorted only, the Mint +authorities refused to take it after they had treated two cakes, one of +119 oz., which yielded only 35 oz. 5 dwt. standard gold, and one of 140 +oz., which gave 41 oz. 10 dwt. The gold smelted on the mine was nearly +as bad proportionately. Thus, 128 oz. smelted down at the Mint to 87 oz. +8 dwt. and 109 oz. to 55 oz. 10 dwt. The impurity was principally +iron, a most unusual thing in my experience, and was due to two causes +revealed by assay of the ore and analysis of the mine water, viz., +an excess of arsenate of iron in the stone, and the presence in large +proportions of mineral salts, principally chloride of Calcium CaCl., +sodium NaCl, and magnesium MgCl2, in the mine water used in the battery. +The exact analysis of the water was as follows:-- + + Carbonate of Iron FeCO3 2.76 grains per gallon + Carbonate of Calcium CaCO3 7.61 grains per gallon + Sulphate of Calcium CaSO4 81.71 grains per gallon + Chloride of Calcium CaCl2 2797.84 grains per gallon + Chloride of Magnesium MgCl2 610.13 grains per gallon + Chloride of Sodium or + Common Salt NaCl 5072.65 grains per gallon + + Total solid matter 8572.70 = 19.5 oz. to the gallon. + +It will be seen, then, that this water is nearly four times more salt +that that of the sea. The effect of using a water of this character, as +I have previously found, is to cause the amalgamation of considerable +quantities of iron with the gold as in this case. + +I received 10 oz. of amalgam, and having found what constituted its +impurities proceeded to experiment as to its treatment. When retorted on +the mine it was turned out in a black cake so impure as almost to +make it impossible to smelt properly. I found the same result on +first retorting, and after a number of experiments which need not be +recapitulated though some were fairly effective, I hit on the following +method, which was found to be most successful and will probably be +so found in other localities where similarly unfavourable conditions +prevail. + +I took a small ball of amalgam, placed it in a double fold of new fine +grained calico, and after soaking in hot water put it under a powerful +press. The weight of the ball before pressing was 1583 gr. From this +383 gr. of mercury was expressed and five-eighths of a grain of gold +was retorted from this expressed mercury. The residue, in the form of a +dark, grey, and very friable cake, was powdered up between the fingers +and retorted, when it became a brown powder; it was afterwards calcined +on a flat sheet in the open air; result, 510 gr. of russet-coloured +powder. Smelted with borax, the iron oxide readily separated with the +slag; result, 311 gr. gold 871-1000 fine; a second smelting brought this +up to 914-1000 fine. Proportion of smelted gold to amalgam, one-fifth. + +The principal point about this mode of treatment is the squeezing out +of the mercury, whereby the amalgam goes into the retort in the form of +powder, thus preventing the slagging of the iron and enclosure of +the gold. The second point of importance is thorough calcining before +smelting. + +Of course it would be practicable, if desired, to treat the powder with +hydrochloric acid, and thus remove all the iron, but in a large way this +would be too expensive, and my laboratory treatment, though necessarily +on a small scale, was intended to be on a practical basis. + +The amalgam at this mine was in this way afterwards treated with great +success. + +For the information of readers who do not understand the chemical +symbols it may be said that + + FeCO3 is carbonate of iron; + CaCO3 is carbonate of calcium; + CaSO4 is sulphate of calcium; + CaCl2 is chloride of calcium; + MgCl2 is chloride of magnesium; + NaCl is chloride of sodium, or common salt. + + + + +CHAPTER VII + +GOLD EXTRACTION--SECONDARY PROCESSES AND LIXIVIATION + +Before any plan is adopted for treating the ore in a new mine the +management should very seriously and carefully consider the whole +circumstances of the case, taking into account the quantity and quality +of the lode stuff to be operated on, and ascertain by analysis what are +its component parts, for, as before stated, the treatment which will +yield most satisfactory results with a certain class of gangue on one +mine will sometimes, even when the material is apparently similar, prove +a disastrous failure in another. Some time since I was glad to note that +the manager of a prominent mine strongly discountenanced the purchase of +any extracting plant until he was fully satisfied as to the character +of the bulk of the ore he would have to treat. It would be well for the +pockets of shareholders and the reputation of managers, if more of our +mine superintendents followed this prudent and sensible course. + +Having treated on gold extraction with mercury by amalgamated plates +and their accessories, something must be said about secondary modes +of saving in connection with the amalgamation process. The operations +described hitherto have been the disintegration of the gold-bearing +material and the extraction therefrom of the coarser free gold. But it +must be understood that most auriferous lode stuff contains a proportion +of sulphides of various metals, wherein a part of the gold, usually in a +very finely divided state, is enclosed, and on this gold the mercury has +no influence. Also many lodes contain hard heavy ferric ores, such as +titanic iron, tungstate of iron, and hematite, in which gold is held. +In others, again, are found considerable quantities of soft powdery iron +oxide or "gossan," and compounds such as limonite, aluminous clay, etc., +which, under the action of the crushing mill become finely divided and +float off in water as "slimes," carrying with them atoms of gold, often +microscopically small. To save the gold in such matrixes as these is an +operation which even the best of our mechanical appliances have not yet +fully accomplished. + +Where there is not too great a proportion of base metals on which the +solvent will act, and when the material is rich enough in gold to pay +for the extra cost of treatment, chlorination or cyanisation are the +best modes of extraction yet practically adopted. + +Presuming, however, that we are working by the amalgamation process, and +have crushed our stone and obtained the free gold, the next requirement +is an effective concentrator. Of these there are many before the +public, and some do excellent work, but do not act equally well in +all circumstances. The first and most primitive is the blanket table, +previously mentioned; but it can hardly be said to be very effective, +and requires constant attention and frequent changing and washing of the +strips of blanket. + +Instead of blanket tables percussion tables are sometimes used, to which +a jerking motion is given against the flow of the water and pulp, and by +this means the heavier minerals are gathered towards the upper part of +the table, and are from thence removed from time to time as they become +concentrated. + +I have seen this appliance doing fairly good work, but it is by no means +a perfect concentrator. + +Another form of "shaking table" is one in which the motion is given +sideways, and this, whether amalgamated, or provided with small riffles, +or covered with blanket, keeps the pulp lively and encourages the +retention of the heavier particles, whether of gold or base metals +containing gold. There has also been devised a rocking table the action +of which is analogous to that of the ordinary miner's cradle. This +appliance, working somewhat slowly, swings on rockers from side to side, +and is usually employed in mills where, owing to the complexity of the +ore, difficulties have been met with in amalgamating the gold. Riffles +are provided and even very fine gold is sometimes effectively recovered +by their aid. + +The Frue vanner will, as a rule, act well when the pulp is sufficiently +fine. It is really a adaptation of an old and simple apparatus used +in China and India for washing gold dust from the sands of rivers. The +original consisted of an endless band of strong cloth or closely woven +matting, run on two horizontal rollers placed about seven feet apart, +one being some inches lower than the other. The upper is caused to +revolve by means of a handle. The cloth is thus dragged upwards against +a small stream of water and sand fed to it by a second man, the first +man not only turning the handle but giving a lateral motion to the band +by means of a rope tied to one side. + +Chinamen were working these forerunners of the Frue vanner forty years +ago in Australia, and getting fair returns. + +The Frue vanner is an endless indiarubber band drawn over an inclined +table, to which a revolving and side motion is given by ingenious +automatic mechanism, the pulp being automatically fed from the upper +end, and the concentrates collected in a trough containing water in +which the band is immersed in its passage under the table; the lighter +particles wash over the lower end. The only faults with the vanner +are--first, it is rather slow; and secondly, though so ingenious it is +just a little complicated in construction for the average non-scientific +operative. + +Of pan concentrators there is an enormous selection, the principle in +most being similar--i.e., a revolving muller, which triturates the sand, +so freeing the tiny golden particles and admitting of their contact with +the mercury. The mistake with respect to most of these machines is the +attempt to grind and amalgamate in one operation. Even when the stone +under treatment contains no deleterious compounds the simple action +of grinding the hard siliceous particles has a bad effect on the +quicksilver, causing it to separate into small globules, which either +oxidising or becoming coated with the impurities contained in the ore +will not reunite, but wash away in the slimes and take with them a +percentage of the gold. As a grinder and concentrator, and in some cases +as an amalgamator, when used exclusively for either purpose, the Watson +and Denny pan is effective; but although successfully used at one mine +I know, the mode there adopted would, for reasons previously given, be +very wasteful in many other mines. + +There is considerable misconception, even among men with some practical +knowledge, as to the proper function of these secondary saving +appliances; and sometimes good machines are condemned because they will +not perform work for which they were never intended. It cannot be too +clearly realized that the correct order of procedure for extracting the +gold held in combination with base metals is--first, reduction of the +particles to a uniform gauge and careful concentration only; next, +the dissipation, usually by simple calcination, of substances in the +concentrates inimical to the thorough absorption of the gold by the +mercury; and lastly, the amalgamation of the gold and mercury. + +For general purposes, where the gangue has not been crushed too fine, +I think the Duncan pan will usually be found effective in saving the +concentrates. In theory it is an enlargement of the alluvial miner's tin +dish, and the motion imparted to it is similar to the eccentric motion +of that simple separator. + +The calcining may be effectively carried out in an ordinary +reverberatory furnace, the only skill required being to prevent over +roasting and so slagging the concentrates; or not sufficiently calcining +so as to remove all deleterious constituents; the subject, however, is +fully treated in Chapter VIII. + +For amalgamating I prefer some form of settler to any further grinding +appliance, but I note also improvements in the rotary amalgamating +barrel, which, though slow, is, under favourable conditions, an +effective amalgamator. The introduction of steam under pressure into an +iron cylinder containing a charge of concentrates with mercury is said +to have produced good results, and I am quite prepared to believe such +would be the case, as we have long known that the application of steam +to ores in course of amalgamation facilitates the process considerably. + +Some seventeen years since I was engaged on the construction of a dry +amalgamator in which sublimated mercury was passed from a retort through +the descending gangue in a vertical cylinder, the material thence +falling through an aperture into a revolving settler, the object being +to save water on mines in dry country. The model, about quarter size, +was completed when my attention was called to an American invention, +in which the same result was stated to be attained more effectively by +blowing the mercury spray through the triturated material by means of +a steam jet. I had already encountered a difficulty, since found so +obstructive by experimentalists in the same direction, that is, +the getting of the mercury back into its liquid metallic form. This +difficulty I am now convinced can be largely obviated by my own device +of using a very weak solution of sulphuric acid (it can hardly be +too weak) and adding a small quantity of zinc to the mercury. It is +perfectly marvellous how some samples of mercury "sickened" or "floured" +by bad treatment, may be brought back to the bright limpid metal by a +judicious use of these inexpensive materials. + +Thus it will probably be found practicable to crush dry and amalgamate +semi-dry by passing the material in the form of a thin pasty mass to a +settler, as in the old South American arrastra, and, by slowly stirring, +recover the mercury, and with it the bulk of the gold. + +The following is from the _Australian Mining Standard_, and was headed +"Amalgamation Without Overflow": + +"Recent experiments at the Ballarat School of Mines have proved that a +deliverance from difficulties is at hand from an unexpected quarter. +The despised Chilian mill and Wheeler pan, discarded at many mines, will +solve the problem, but the keynote of success is amalgamation without +overflow. Dispense with the overflow and the gold is saved. + +"Two typical mines--the Great Mercury Proprietary Gold Mine, of +Kuaotunu, N.Z., the other, the Pambula, N.S.W.--have lately been +conducting a series of experiments with the object of saving their fine +gold in an economical manner. The last and best trials made by these +companies were at the Ballarat School of Mines, where amalgamation +without overflow was put to a crucial test, in each case with the +gratifying result that ninety-six per cent of the precious metal was +secured. What this means to the Great Mercury Mine, for instance, can +easily be imagined when it is understood that notwithstanding all the +latest gold-saving adjuncts during the last six months 1260 tons of ore, +worth 4l. 17s. 10 2_3d. a ton, have been put through for a saving of 1l. +9s. 1 2_3d. only; or in other words over two-thirds of the gold has gone +to waste (for the time being) in the tailings, and in the tailings +at the present moment lie the dividends that should have cheered +shareholders' hearts. + +"And now for the _modus operandi_, which, it must be remembered, is not +hedged in by big royalties to any one, rights, patent or otherwise. The +ore to be treated is first calcined, then put through a rock-breaker +or stamper battery in a perfectly dry state. If the battery is used, +ordinary precautions, of course, must be taken to prevent waste, or the +dust becoming obnoxious to the workmen. The ore is then transferred +to the Chilian mill and made to the consistency of porridge, the +quicksilver being added. When the principal work of amalgamation is done +(experience soon teaching the amount of grinding necessary), from the +Chilian mill the paste (so to say) is passed to a Wheeler or any +other good pan of a similar type, when the gold-saving operation is +completed." + +This being an experiment in the same direction as my own, I tried it on +a small scale. I calcined some very troublesome ore till it was fairly +"sweet," triturated it, and having reduced it with water to about the +consistency of invalid's gruel, put it into a little berdan pan made +from a "camp oven," which I had used for treating small quantities of +concentrates, and from time to time drove a spray of mercury, wherein a +small amount of zinc had been dissolved, into the pasty mass by means +of a steam jet, added about half an ounce of sulphuric acid and kept the +pan revolving for several hours. The result was an unusually successful +amalgamation and consequent extraction--over ninety per cent. + +Steam--or to use the scientific term, hydro-thermal action--has played +such an important part in the deposition of metals that I cannot but +think that under educated intelligence it will prove a powerful agent +in their extraction. About fourteen years ago I obtained some rather +remarkable results from simply boiling auriferous ferro-sulphides in +water. There is in this alone an interesting, useful, and profitable +field for investigation and experiment. + +The most scientific and perfect mode of gold extraction (when the +conditions are favourable) is lixiviation by means of chlorine, +potassium cyanide, or other aurous solvent, for by this means as much as +98 per cent of the gold contained in suitable ores can be converted into +its mineral salt, and being dissolved in water, re-deposited in metallic +form for smelting; but lode stuff containing much lime would not be +suitable for chlorination, or the presence of a considerable proportion +of such a metal as copper, particularly in metallic form, would be fatal +to success, while cyanide of potassium will also attack metals other +than gold, and hence discount the effect of this solvent. + +The earlier practical applications of chlorine to gold extraction were +known as Mears' and Plattner's processes, and consisted in placing the +material to be operated on in vats with water, and introducing chlorine +gas at the bottom, the mixture being allowed to stand for a number +of hours, the minimum about twelve, the maximum forty-eight. The +chlorinated water was then drawn off containing the gold in solution +which was deposited as a brown powder by the addition of sulphate of +iron. + +Great improvements on this slow and imperfect method have been made of +late years, among the earlier of which was that of Messrs. Newbery +and Vautin. They placed the pulp with water in a gaslight revolving +cylinder, into which the chlorine was introduced, and atmospheric air to +a pressure of 60 lb. to the square inch was pumped in. The cylinder with +its contents was revolved for two hours, then the charge was withdrawn +and drained nearly dry by suction, the resultant liquid being slowly +filtered through broken charcoal on which the chloride crystals were +deposited, in appearance much like the bromo-chlorides of silver ore +seen on some of the black manganic oxides of the Barrier silver +mines. The charcoal, with its adhering chlorides, was conveyed to the +smelting-house and the gold smelted into bars of extremely pure metal. +Messrs. Newbery and Vautin claimed for their process decreased time for +the operation with increased efficiency. + +At Mount Morgan, when I visited that celebrated mine, they were using +what might be termed a composite adaptation process. Their chlorination +works, the largest in the world, were putting through 1500 tons per +week. The ore as it came from the mine was fed automatically into Krom +roller mills, and after being crushed and sifted to regulation gauge was +delivered into trucks and conveyed to the roasting furnaces, and thence +to cooling floors, from which it was conveyed to the chlorinating +shed. Here were long rows of revolving barrels, on the Newbery-Vautin +principle, but with this marked difference, that the pressure in the +barrel was obtained from an excess of the gas itself, generated from a +charge of chloride of lime and sulphuric acid. On leaving the barrels +the pulp ran into settling vats, somewhat on the Plattner plan, and +the clear liquid having been drained off was passed through a charcoal +filter, as adopted by Newbery and Vautin. The manager, Mr. Wesley Hall, +stated that he estimated cost per ton was not more than 30s., and he +expected shortly to reduce that when he began making his own sulphuric +acid. As he was obtaining over 4 oz. to the ton the process was paying +very well, but it will be seen that the price would be prohibitive for +poor ores unless they could be concentrated before calcination. + +The Pollok process is a newer, and stated to be a cheaper mode of +lixiviation by chlorine. It is the invention of Mr. J. H. Pollok, of +Glasgow University, and a strong Company was formed to work it. With him +the gas is produced by the admixture of bisulphate of sodium (instead +of sulphuric acid, which is a very costly chemical to transport) +and chloride of lime. Water is then pumped into a strong receptacle +containing the material for treatment and powerful hydraulic pressure is +applied. The effect is stated to be the rapid change of the metal into +its salt, which is dissolved in the water and afterwards treated with +sulphate of iron, and so made to resume its metallic form. + +It appears, however, to me that there is no essential difference in the +pressure brought to bear for the quickening of the process. In each case +it is an air cushion, induced in the one process by the pumping in of +air to a cylinder partly filled with water, and in the other by pumping +in water to a cylinder partly filled with air. + +The process of extracting gold from lode stuff and tailings by means +of cyanide of potassium is now largely used and may be thus briefly +described:--It is chiefly applied to tailings, that is, crushed ore +that has already passed over the amalgamating and blanket tables. The +tailings are placed in vats, and subjected to the action of solutions +of cyanide of potassium of varying strengths down to 0.2 per cent. These +dissolve the gold, which is leached from the tailings, passed through +boxes in which it is precipitated either by means of zinc shavings, +electricity, or to the precipitant. The solution is made up to its +former strength and passed again through fresh tailings. When the +tailings contain a quantity of decomposed pyrites, partly oxidised, the +acidity caused by the freed sulphuric acid requires to be neutralised by +an alkali, caustic soda being usually employed. + +When "cleaning up," the cyanide solution in the zinc precipitating boxes +is replaced by clean water. After careful washing in the box, to cause +all pure gold and zinc to fall to the bottom, the zinc shavings are +taken out. The precipitates are then collected, and after calcination in +a special furnace for the purpose of oxidising the zinc, are smelted in +the usual manner. + +The following description of an electrolytic method of gold deposition +from a cyanide solution was given by Mr. A. L. Eltonhead before the +Engineers' Club of Philadelphia. + +A description of the process is as follows:--"The ore is crushed to a +certain fineness, depending on the character of the gangue. It is then +placed in leaching vats, with false bottoms for filtration, similar +to other leaching plants. A solution of cyanide of potassium and other +chemicals of known percentage is run over the pulp and left to stand +a certain number of hours, depending on the amount of metal to be +extracted. It is then drained off and another charge of the same +solution is used, but of less strength, which is also drained. The pulp +is now washed with clean water, which leaches all the gold and silver +out, and leaves the tailings ready for discharge, either in cars or +sluiced away by water, if it is plentiful. + +"The chemical reaction of cyanide of potassium with gold is as follows, +according to Elsner:-- + +2Au + 4KCy + O + H2O = 2KAuCy2 + 2KHO. + +"That is, a double cyanide of gold and potassium is formed. + +"All filtered solutions and washings from the leaching vats are saved +and passed through a precipitating 'box' of novel construction, which +may consist either of glass, iron or wood, and be made in any shape, +either oval, round, or rectangular--if the latter, it will be about 10 +ft. long, 4 ft. wide and 1 ft. high--and is partitioned off lengthwise +into five compartments. Under each partition, on the inside or bottom of +the 'box,' grooves may be cut a quarter-to a half-inch deep, extending +parallel with the partitions to serve as a reservoir for the amalgam, +and give a rolling motion to the solution as it passes along and through +the four compartments. The centre compartment is used to hold the lead +or other suitable anode and electrolyte. + +"The anode is supported on a movable frame or bracket, so it may be +moved either up or down as desired, it being worked by thumb-screws at +each end. + +"The electrolyte may consist of saturated solutions of soluble alkaline +metals and earth. The sides or partitions of each compartment dip into +the mercury, which must cover the 'box' evenly on the bottom to the +depth of about a half-inch. + +"Amalgamated copper strips or discs are placed in contact with the +mercury and extended above it, to allow the gold and silver solution of +cyanide to come in contact. + +"The electrodes are connected with the dynamo; the anode of lead being +positive and the cathode of mercury being negative. The dynamo is +started, and a current of high amperage and low voltage is generated, +generally 100 to 125 amperes, and with sufficient pressure to decompose +the electrolyte between the anode and the cathode. + +"As the gas is generated at the anode, a commotion is created in the +liquid, which brings a fresh and saturated solution of electrolyte +between the electrodes for electrolysis, and makes it continuous in its +action. + +"The solution of double cyanide of gold, silver, and potassium, which +has been drained from the leaching vats, is passed over the mercury in +the precipitating 'box' when the decomposition of the electrolyte by the +electric current is being accomplished, the gold and silver are set +free and unite with the mercury, and are also deposited on the plates or +discs of copper, forming amalgam, which is collected and made marketable +by the well known and tried methods. The above solution is regenerated +with cyanide of potassium by the setting free of the metals in the +passage over the 'box.' + +"In using this solution again for a fresh charge of pulp, it is +reinforced to the desired percentage, or strengthened with cyanide +of potassium and other chemicals, and is always in good condition for +continuing the operation of dissolving. + +"The potassium acting on the water of the solution creates nascent +hydrogen and potassium hydrate; the nascent hydrogen sets free the +metals (gold and silver), which are precipitated into the mercury and +form amalgam, leaving hydrocyanic acid; this latter combines with +the potassium hydrate of the former reaction, thus forming cyanide of +potassium. There are other reactions for which I have not at present the +chemical formulas. + +"As the solution passes over the mercury, the centre compartment of the +'box' is moved slowly longitudinally, which spreads the mercury, the +solution is agitated and comes in perfect contact with the mercury, as +well as the amalgamated plates or discs of copper, ensuring a perfect +precipitation. + +"It is not always necessary to precipitate all the gold and silver from +the solution, for it is used over and over again indefinitely; but when +it is required, it can be done perfectly and cheaply in a very short +time. + +"No solution leached from the pulp, containing cyanide of potassium, +gold and silver, need be run to waste, which is in itself an enormous +saving over the use of zinc shavings when handling large quantities of +pulp and solution. + +"Some of the advantages the electro-chemical process has over other +cyanide processes are: Its cleanliness, quickness of action, cheapness, +and large saving of cyanide of potassium by regeneration; not wasting +the solutions, larger recovery of the gold and silver from the +solutions; the cost of recovery less; the loss of gold, silver, and +cyanide of potassium reduced to a minimum; the use of caustic alkali in +such quantity as may be desired to keep the cyanide solution from +being destroyed by the solidity of the pulp, and also sometimes to give +warmth, as a warm cyanide solution will dissolve gold and silver quicker +than a cold one. These caustic alkalies do not interfere with or prevent +the perfect precipitation of the metals. The bullion recovered in this +process is very fine, while the zinc-precipitated bullion is only about +700 fine. + +"The gold and silver is dissolved, and then precipitated in one +operation, which we know cannot be done in the 'chlorination +process'; besides, the cost of plant and treatment is much less in the +above-described process. + +"The electro-chemical process, which I have hastily sketched will, I +think, be the future cheap method of recovering fine or flour gold from +our mines and waste tailings or ore dumps. + +"Without going into details of cost of treatment, I will state that with +a plant of a capacity of handling 10,000 tons of pulp per month, +the cost should not exceed 8s. per ton, but that may be cheapened by +labour-saving devices. There being no expensive machinery, a plant could +be very cheaply erected wherever necessary." + + + +CHAPTER VIII + +CALCINATION OR ROASTING OF ORES + +The object of calcining or roasting certain ores before treatment is +to dissipate the sulphur or sulphides of arsenic, antimony, lead, +etc., which are inimical to treatment, whether by ordinary mercuric +amalgamation or lixiviation. The effect of the roasting is first to +sublimate and drive off as fumes the sulphur and a proportion of the +objectionable metals. What is left is either iron oxide, "gossan," or +the oxides of the other metals. Even lead can thus be oxidised, but +requires more care as it melts nearly as readily as antimony and is +much less volatile. The oxides in the thoroughly roasted ore will not +amalgamate with mercury, and are not acted on by chlorine or cyanogen. + +To effect the oxidation of sulphur, it is necessary not only to bring +every particle of sulphur into contact with the oxygen of the air, but +also to provide adequate heat to the particles sufficient to raise them +to the temperature that will induce oxidation. No appreciable effect +follows the mere contact of air with sulphur particles at atmospheric +temperature; but if the particles be raised to a temperature of 500 +degrees Fahr., the sulphur is oxidised to the gaseous sulphur dioxide. +The same action effects the elimination of the arsenic and antimony +associated with gold and silver ores, as when heated to a certain +constant temperature these metals readily oxidise. + +The science of calcination consists of the method by which the sulphide +ores, having been crushed to a proper degree of fineness, are raised +to a sufficient temperature and brought into intimate contact with +atmospheric air. + +It will be obvious then that the most effective method of roasting +will be one that enables the particles to be thoroughly oxidised at the +lowest cost in fuel and in the most rapid manner. + +The roasting processes in practical use may be divided into three +categories: + +_First or A Process._--Roasting on a horizontal and stationary hearth, +the flame passing over a mass of ore resting on such hearth. In order to +expose the upper surface of the ore to contact with air the material is +turned over by manual labour. This furnace of the reverberatory type is +provided with side openings by which the turning over of the ore can +be manually effected, and the new ore can be charged and afterwards +withdrawn. + +_Second or B Process._--Roasting in a revolving hearth placed at a +slight incline angle from the horizontal. The furnace is of cylindrical +form and is internally lined with refractory material. It has +projections that cause the powdered ore to be lifted above the flame, +and, at a certain height, to fall through the flame and so be rapidly +raised to the temperature required to effect the oxidation of the +oxidisable minerals which it is desired to extract. + +The rate, or speed, of revolution of this revolving furnace obviously +depends upon the character of the ore under treatment; it may vary from +two revolutions per minute down to one revolution in thirty minutes. Any +kind of fuel is available, but that of a gaseous character is stated to +be by far the most efficient. + +Any ordinary cylinder of a length of 25 ft., and a diameter of 4 ft. 6 +in., inclined 1 ft. 6 in. in its length, will calcine from 24 to 48 tons +per diem. + +Another form of rotating furnace is one in which the axis is horizontal. +It is much shorter than the inclined type, and the feeding and removal +of the ore is effected by the opening of a retort lid door provided at +the side of the furnace. Openings provided at each end of the furnace +permit the passage of the flame through it, and the revolution of the +furnace turns over the powdered ore and brings it into more or less +sustained contact with the oxidising flame. The exposure of the ore to +this action is continued sufficiently long to ensure the more or less +complete oxidation of the ore particles. + +_Third or C Process._--In this process the powdered ore is allowed to +fall in a shower from a considerable height, through the centre of a +vertical shaft up which a flame ascends; the powdered ore in falling +through the flame is heated to an oxidising temperature, and the +sulphides are thus depleted of their sulphur and become oxides. + +Another modification of this direct fall or shaft furnace is that in +which the fall of the ore is checked by cross-bars or inclined plates +placed across the shaft; this causes a longer oxidising exposure of the +ore particles. + +When the sulphur contents of pyritous ores are sufficiently high, and +after the ore has been initially fired with auxiliary carbonaceous fuel, +it is unnecessary, in a properly designed roasting furnace, to add +fuel to the ore to enable the heat for oxidation to be obtained. The +oxidation or burning of the sulphur will provide all the heat necessary +to maintain the continuity of the process. The temperature necessary for +effecting the elimination of both sulphur and arsenic is not higher +than that equivalent to dull red heat; and provided that there is a +sufficient mass of ore maintained in the furnace, the potential heat +resulting from the oxidation of the sulphur will alone be adequate to +provide all that is necessary to effect the calcination. + + +TYPES OF FURNACES OF THE DIFFERENT CLASSES THAT ARE IN ACTUAL USE. + +"A" OR REVERBERATORY CLASS. + +The construction of this furnace has already been sufficiently +described. If the roasting is performed in a muffle chamber, the +arrangement employed by Messrs. Leach and Neal, Limited, of Derby, and +designed by Mr. B. H. Thwaite, C.E., can be advantageously employed in +this furnace, which is fired with gaseous fuel. The sensible heat of the +waste gases is utilised to heat the air employed for combustion; and by +a controllable arrangement of combustion, a flame of over 100 feet in +length is obtained, with the result that the furnace from end to end is +maintained at a uniform temperature. By this system, and with gaseous +fuel firing, a very considerable economy in fuel and in repairs to +furnace, and a superior roasting effect, have been obtained. + +Where the ordinary reverberatory hearth is fired with solid coal from +an end grate, the temperature is at its maximum near the firing end, and +tails off at the extreme gas outlet end. The ores in this furnace should +therefore be fed in at the colder end of the hearth and be gradually +worked or "rabbled" forward to the firing end. + +One disadvantage of the reverberatory furnace is the fact that it is +impossible to avoid the incursion of air during the manual rabbling +action, and this tends to cool the furnace. + +The cost of roasting, to obtain the more or less complete oxidation, or +what is known in mining parlance as a "sweet roast" (because a perfectly +roasted ore is nearly odourless) varies considerably, the variation +depending of course upon the character of the ore and the cost of labour +and fuel. + +There are several modifications of the reverberatory furnace in use, +designed mechanically to effect the rabbling. One of the most successful +is that known as the Horse-shoe furnace. In plan the hearth of the +furnace resembles a horse-shoe. + +The stirring of the ore over the hearth is effected by means of +carriages fixed in the centre of the furnace and having laterally +projecting arms, carrying stirrers, that move along the hearth and turn +over the pulverised ore. + +In operation, half the carriages are traversing the furnace, and half +are resting in the cooling space, so that a control over the temperature +of the stirrers is established. + +This furnace is stated to be more economical in labour than other +mechanically stirred reverberatory furnaces, and there is also said to +be an economy in fuel. + +Usually the mechanical stirring furnaces give trouble and should be +avoided, but the horse-shoe type possesses qualifications worthy of +consideration. + +"B."--THE REVOLVING CYLINDER FURNACE. + +Of these the best known to me are: The Howell-White, the Bruckner, the +Thwaite-Denny, and the Molesworth. + +The Bruckner is a cylinder, turning on the horizontal axis and carried +by four rollers. + +The batch of ore usually charged into the two charging hoppers weighs +about four tons. When the two charging doors are brought under the +hopper mouth, the contents of the hopper fall directly into the +cylinder. + +The ends or throats of the furnace are reduced just sufficiently to +allow the flame evolved from a grated furnace to pass completely through +the cylinder. + +A characteristic size for this Bruckner furnace is one having a length +of 12 feet and a diameter of 6 feet. A furnace of this capacity will +have an inclusive weight (iron and brickwork) of 15 tons. + +The time of operation, with the Bruckner, will vary with the character +of the ore under treatment and the nature of the fuel employed. Four +hours is the minimum and twelve hours should be the maximum time of +operation. + +By the addition of common salt with the batch of ore, such of its +constituents as are amenable to the action of chlorine are chlorinated +as well as freed from sulphur. + +Where the ore contains any considerable quantity of silver which should +be saved, the addition of the salt is necessary as the silver is very +liable to become so oxidised in the process of roasting as to render +its after treatment almost impossible. I know a case in point where an +average of nearly five ounces of silver to the ton, at that time worth +30s., was lost owing to ignorance on this subject. Had the ore been +calcined with salt, NaCl, the bulk of this silver would have been +amalgamated and thus saved. It was the extraordinary fineness of the +gold saved by amalgamation as against my tests of the ore by fire assay +that put me on the track of a most indefensible loss. + +_The Howell-White Furnace._--This furnace consists of a cast iron +revolving cylinder, averaging 25 feet in length and 4 ft. 4 in. in +diameter, which revolves on four friction rollers, resting on truck +wheels, rotated by ordinary gearing. + +The power required for effecting the revolution should not exceed four +indicated horse-power. + +The cylinder is internally lined with firebrick, projecting pieces +causing the powdered ore to be raised over the flame through which it +showers, and is thereby subjected to the influence of heat and to direct +contact oxidation. + +The inclination of the cylinder, which is variable, promotes the gradual +descension of the ore from the higher to the lower end. It is fed into +the upper end, by a special form of feed hopper, and is discharged into +a pit at the lower end, from which the ore can be withdrawn at any time. + +The gross weight of the furnace, which is, however, made in segments to +be afterwards bolted together, is some ninety to one hundred tons. + +The furnace is fired with coal on a grated hearth, built at the lower +end; it is more economical both in fuel and in labour than an ordinary +reverberatory furnace. + +_The Thwaite-Denny Revolving Furnace._--This new type of furnace, which +is fired with gaseous fuel, is stated to combine the advantages of the +Stetefeldt, the Howell-White, and the Bruckner. + +It is constructed as follows:--Three short cylinders, conical in shape +and of graduated dimensions, are superimposed one over the other, their +ends terminating in two vertical shafts of brickwork, by which the three +cylinders are connected. The powdered ore is fed into the uppermost +cylinder and gravitates through the series. The highest cylinder is the +largest in diameter, the lowest the smallest. + +The gas flame, burnt in a Bunsen arrangement, enters the smallest end +of the lowest cylinder and passes through it; then returns through the +series and the ore is reduced by the expulsion of its sulphur, arsenic, +etc., as it descends from the top to the bottom. The top cylinder is +made larger than the one below it and the middle cylinder is made larger +than the lowest one in proportion to the increased bulk of gases and +ore. + +The powdered ore in descending through the cylinders is lifted up and +showers through the flame, falling in its descent a distance of over +1000 feet. By the time it reaches the bottom the ore is thoroughly +roasted. + +Provision is made for the introduction of separate supplies of air +and gas into each cylinder; this enables the oxidising treatment to be +controlled exactly as desired so as to effect the best results with all +kinds of ore. Each cylinder is driven from its own independent gearing, +and the speed of each cylinder can be varied at will. + +The output of this type of furnace, the operations of which appear to be +more controllable than those of similar appliances, depends, of course, +upon the nature of the ore, but may be considered to range within the +limits of twelve to fifty tons in twenty-four hours, and the cost of +roasting will vary from 2s. 6d. to 4s. per ton, depending upon the +quality of ore and of fuel. + +The gaseous fuel generating system permits not only the absolute control +over the temperature in the furnace, but the use of the commonest kinds +of coal, and even charcoal is available. + +The power required to drive the Thwaite-Denny furnace is four indicated +horse-power. + +_The Molesworth Furnace_ also is a revolving cylindrical appliance, +which, to say the least of it, is in many respects novel and ingenious. +It consists of a slightly cone-shaped, cast-iron cylinder about fourteen +feet long, the outlet end being the larger to allow for the expansion of +the gases. Internal studs are so arranged as to keep the ore agitated; +and spiral flanges convey it to the outlet end continually, shooting +it across the cylinder. The cylinder is encased in a brick furnace. The +firing is provided from _outside_, the inventor maintaining that the +products of combustion are inimical to rapid oxidisation, to specially +promote which he introduces an excess of oxygen produced in a small +retort set in the roof of the furnace and fed from time to time with +small quantities of nitrate of soda and sulphuric acid. Ores containing +much sulphur virtually calcine themselves. I have seen this appliance +doing good work. The difficulties appeared to be principally mechanical. + +There are other furnaces which work with outside heat, but I have not +seen them in action. + +"C."--SHAFT TYPE OF FURNACE + +In one form of this furnace, instead of allowing the ore to descend in +a direct clear fall the descent is impeded by inclined planes placed at +different levels in the height of the shaft, the ore descending from one +plane to the other. + +_The Stetefeldt Shaft Furnace._--Although very expensive in first cost, +has many advantages. No motive power is required and the structure of +the furnace is of a durable character. Its disadvantages are:--Want +of control, and the occasionally imperfect character of the roasting +originating therefrom. + +Three sizes of Stetefeldt's furnaces are constructed: + +The largest will roast from 40 to 80 tons per diem. + +The intermediate will roast from 20 to 40 tons per diem. + +The smallest will roast from 10 to 20 tons per diem. + +A good furnace should bring down the sulphur contents even of +concentrates so as to be innocuous to mercuric amalgamation. The sulphur +left in the ore should never be allowed to exceed two per cent. + +A forty per cent pyritous or other sulphide ore should be roasted in a +revolving furnace in thirty to forty minutes, and without any auxiliary +fuel. + +For ordinary purposes a 40-foot chimney is adequate for furnace work; +such a chimney four feet square inside at the base, tapering to 2' 6" at +the summit, will require 12,000 red bricks, and 1500 fire-bricks for +an internal lining to a height of 12 feet from the base of the chimney +shaft. + +When second-hand Lancashire or Cornish boiler flues are available, they +make admirable and inexpensive chimneys. The advantage of wrought-iron +or steel chimneys lies in the convenience of removal and erection. They +should be made in sections of 20 feet long, three steel wire guy-ropes +attached to a ring, riveted to a ring two-thirds of the height of the +chimney, and attached to holdfasts driven into the ground; tightening +couplings should be provided for each wire. + +Flue dust depositing chambers should be built in the line of the flues +between the furnace and the chimney; they consist simply of carefully +built brick chambers, with openings to enable workmen to enter and +rapidly clear away the deposited matters. The chambers, three or four +times the cross sectional area of the chimney flue, and ten to twenty +feet long, can be built of brickwork, set in cement; the walls are +provided with a cavity, filled with sand or Portland cement, so that +there will be no danger of the incursion of air. In all furnace work +the greatest possible precautions should be taken to prevent the least +cracking of either joints or bricks. It is surprising how much the +inadequate draft of a good chimney is due to cracks or orifices in the +flues; and therefore a competent furnace-man should see to it that his +flues are thoroughly sound, and free from openings through which the air +can enter.[*] + + [*] For full details of the most recent improvements in the + cyanide process and in other methods of extraction, the + reader is referred to Dr. T. K. Rose's "Metallurgy of Gold," + third edition. + + + + +CHAPTER IX + +MOTOR POWER AND ITS TRANSMISSION + +It is unnecessary to describe methods by which power for mining purposes +has been obtained--that is, up to within the last five years--beyond +a general statement, that when water power has been available in the +immediate locality of the mine, this cheap natural source of power has +been called upon to do duty. Steam has been the alternative agent of +power production applied in many different ways, but labouring under as +many disadvantages, chief of which are lack of water, scarcity of fuel +and cost of transit of machinery. Sometimes condensing steam-engines +have been employed. For the generation of steam the semi-portable and +semi-tubular have been the type of boiler that has most usually been +brought into service. Needless to say, when highly mineralised mine +water only is available the adoption of this class of boiler is attended +with anything but satisfactory results. + +Recently, however, there is strong evidence that where steam is the +power agent to be employed the water-tube type of boiler is likely to be +employed, and to the exclusion of all other forms of apparatus for +the generation of steam. The advantages of this type, particularly the +tubulous form (or a small water tube), made as it is in sections, offers +unrivalled facilities for transport service. The heaviest parts need +not exceed 3 cwt. in weight, and require neither heavy nor yet expensive +brickwork foundations. + + +WATERLESS POWER. + +The difficulties in finding water to drive a steam plant are often of +such a serious character as to involve the abandonment of many payable +mines; therefore, a motive power that does not require the aqueous agent +will be a welcome boon. + +It will be a source of gratification to many a gold-claim holder to know +that practical science has enabled motive power to be produced without +the necessity of water, except a certain very small quantity, which once +supplied will not require to be renewed, unless to compensate for the +loss due to atmospheric evaporation. + +Any carbonaceous fuel, such as, say, lignite, coal, or charcoal, can be +employed. The latter can be easily produced by the method described +in the Chapter on "Rules of Thumb," or by building a kiln by piling +together a number of trunks of trees, or fairly large-sized branches, +cut so that they can be built up in a compact form. The pile, after +being covered with earth, is then lighted from the base, and if there +are no inlets for the air except the limited proportion required for the +smouldering fire at the base, the whole of the timber will be gradually +carbonised to charcoal of good quality, which is available for the +waterless power plant. + +The waterless power plant consists of two divisions: First, a gas +generating plant; secondly, an internal combustion or gas engine in +which the gas is burnt, producing by thermo-dynamic action the motive +power required. The system known as the Thwaite Power Gas System is not +only practically independent of the use of water, but its efficiency in +converting fuel heat into work is so high that no existing steam plant +will be able to compete with it. + +The weight of raw timber, afterwards to be converted into charcoal, that +will be required to produce an effective horse-power for one hour equals +7 lb. + +If coal is the fuel 1 1/3 lb. per E.H.P. for one hour's run. + +If lignite is the fuel 2 1/2 lb. per E.H.P. for one hour's run. + +The plant is simple to work, and as no steam boiler is required the +danger of explosions is removed. No expensive chimney is necessary for +the waterless power plant. + +Where petroleum oil can be cheaply obtained, say for twopence per +gallon, one of the Otto Cycle Oil Engines, for powers up to 20 indicated +horse-power, can be advantageously employed. + +These engines have the advantage of being a self-contained power, +requiring neither chimney nor steam boiler, and may be said to be a +waterless power. The objection is the necessity to rely upon oil as +fuel, and the dangers attending the storage of oil. A good oil engine +should not require to use more than a pint of refined petroleum per +indicated horse-power working for one hour. + +Fortunately for the mining industry electricity, that magic and +mysterious agency, has come to its assistance, in permitting motive +power to be transmitted over distances of even as much as 100 miles with +comparatively little loss of the original power energy. + +Given, that on a coal or lignite field, or at a waterfall, 100 +horse-power is developed by the combustion of fuel or by the fall of +water driving a turbine, this power can be electrically transmitted to a +mine or GROUP OF MINES, say 100 miles away, with only a loss of some 30 +horse-power. For twenty miles the loss on transmission should not exceed +15 horse-power so that 70 and 85 horse-power respectively are available +at the mines. No other system offers such remarkable efficiencies of +power transmission. The new Multiphase Alternating Electric Generating +and Power Transmission System is indeed so perfect as to leave +practically no margin for improvement. + +The multiphase electric motor can be directly applied to the stamp +battery and ore-breaker driving-shaft and to the shaft of the +amalgamating pans. + + APPROXIMATE POWER REQUIRED TO DRIVE THE MACHINERY OF A MINE. + + Rock breaker 10 effective horse-power + Amalgamating pan 5 effective horse-power + Grinding pan 6 effective horse-power + Single stamp of 750 lb. dropping + 90 times per minute 1.25 effective horse-power + Settlers 4 effective horse-power + Ordinary hoisting lift 20 effective horse-power + + Allow 10 per cent in addition for overcoming friction. + +Besides this electrical distribution power, which should not cost more +than three farthings per effective horse-power per hour, the electrical +energy can be employed for lighting the drives and the shafts of the +mine. The modern electrical mine lamps leave little to be desired. Also +it is anticipated that once the few existing difficulties have been +surmounted electric drilling will supplant all other methods. + +Electric power can be employed for pumping, for shot firing, for +hauling, and for innumerable purposes in a mine. + +Electricity lends itself most advantageously to so many and varied +processes, even in accelerating the influence of cyanide solutions on +gold, and in effecting the magnetic influence on metallic particles +in separating processes; while applied to haulage purposes, either on +aerial lines or on tram or railroads, it is an immediate and striking +success. + +It is anticipated that in the near future the mines on the Randt, South +Africa, will be electrically driven from a coalfield generating station +located on the coalfields some thirty miles from Johannesburg. Such +a plant made up of small multiples of highly efficient machines will +enable mine-owners to obtain a reliable power to any extent at immediate +command and at a reasonable charge in proportion to the power used. This +wholesale supply of power will be a godsend to a new field, enabling the +opening up to be greatly expedited; and no climatic difficulties, such +as dry seasons, or floods, need interfere with the regular running of +the machinery. The same system of power-generation at a central station +is to be applied to supply power to the mines of Western Australia. + + + +CHAPTER X + +COMPANY FORMATION AND OPERATIONS + +All the world over, the operation of winning from the soil and rendering +marketable the many valuable ores and mine products which abound is +daily becoming more and more a scientific business which cannot be too +carefully entered into or too skilfully conducted. The days of the +dolly and windlass, of the puddler, cradle, and tin dish, are rapidly +receding; and mining, either in lode or alluvial working, is being more +generally recognised as one of the exact sciences. In the past, mining +has been carried on in a very haphazard fashion, to which much of its +non-success may be attributed. + +But the dawn of better days has arrived, and with the advent of schools +of mines and technical colleges there will in future be less excuse for +ignorance in this most important industry. + +This chapter will be devoted to Company formation and working, in which +mistakes leading to very serious consequences daily occur. + +It is not necessary to go deeply into the question why, in the mining +industry more than any other, it should be deemed desirable as a general +rule to carry on operations by means of public Companies, but, as a +matter of fact, few names can be mentioned of men who mine extensively +single handed. Yet, risky as it is, mining can hardly be said to be more +subject to unpreventable vicissitudes than, say, pastoral pursuits, in +which private individuals risk, and often lose or make, enormous sums of +money. + +However, it is with Mining Companies we are now dealing, and with the +errors made in the formation and after conduct of these Associations. + +The initial mistake most often made is that sufficient working capital +is not called up or provided in the floating of the Company. Promoters +trust to get sufficient from the ground forthwith to ensure further +development; the consequence being that, as nearly 99 per cent of mining +properties require a very considerable expenditure of capital before +permanent profits can be relied on, the inexperienced shareholders who +started with inflated hopes of enormous returns and immediate dividends +become disheartened and forfeit their shares by refusing to pay calls, +and thus many good properties are sacrificed. In England, the companies +are often floated fully paid-up, but the same initial error of providing +too little money for the equipment and effective working of the mine is +usually fallen into. + +Again, far too many Companies are floated on the report of some +self-styled mining expert, often a man, who, like the schoolmaster of +the last century, has qualified for the position by failing in every +other business he has attempted. These men acquire a few geological and +mining phrases, and by more or less skilfully interlarding these with +statements of large lodes and big returns they supply reports seductive +enough to float the most worthless properties and cause the waste of +thousands of pounds. But the trouble does not end here. + +When the Company is to be formed, some lawyer, competent or otherwise, +is instructed to prepare articles of association, rules, etc.; which, +three times out of four, is accomplished by a liberal employment +of scissors and paste. Such rules may, or may not, be suited to the +requirements of the organisation. Generally no one troubles much about +the matter, though on these rules depends the future efficient working +of the Company, and sometimes its very existence. + +Then Directors have to be appointed, and these are seldom selected +because of any special knowledge of mining they may possess, but as a +rule simply because they are large shareholders or prominent men whose +names look well in a prospectus. These gentlemen forthwith engage a +Secretary, usually on the grounds that he is the person who has tendered +lowest, to provide office accommodation and keep the accounts; and not +from any particular knowledge he has of the true requirements of the +position. + +The way in which some Directors contrive to spend their shareholders' +money is humorously commented on by a Westralian paper which describes +a great machinery consignment lately landed in the neighbourhood of the +Boulder Kalgoorlie. + +"It would seem as if the purchaser had been let loose blindfold in a +prehistoric material-founder's old iron yard, and having bought up the +whole stock, had shipped it off. The feature of the entire antediluvian +show is the liberal allowance of material devoted to destruction. +Massive kibbles, such as were used in coal mines half a century ago, are +arranged alongside a winding engine, built in the middle of the century, +and evidently designed for hauling the kibbles from a depth of 1000 +feet. Nothing less than horse-power will stir the trucks for underground +use, and their design is distinctly of the antique type. The engine +is built to correspond--of a kind that might have served to raise into +position the pillars of Baalbec, and the mass of metal in it fairly +raises a blush to the iron cheek of frailer modern constructions. The +one grand use to which this monster could be put would be to employ it +as a kedge for the Australian continent in the event of it dragging its +present anchors and drifting down south, but as modern mining machinery +the whole consignment is worth no more than its value as scrap-iron, +which in its present position is a fraction or two less than nothing." + +Next, a man to manage the mine has to be obtained, and some one is +placed in charge, of whose capabilities the Directors have no direct +knowledge. Being profoundly ignorant of practical mining they are +incompetent to examine him as to his qualifications, or to check his +mode of working, so as to ascertain whether he is acting rightly or +not. All they have to rely on are some certificates often too carelessly +given and too easily obtained. Finally, quite a large proportion of the +allottees of shares have merely applied for them with the intention of +selling out on the first opportunity at a premium, hence they have no +special interest in the actual working of the mine. + +Now let us look at the prospects of the Association thus formed. The +legal Manager or Secretary, often a young and inexperienced man, knows +little more than how to keep an ordinary set of books, and not always +that. He is quite ignorant of the actual requirements of the mine, or +what is a fair price to pay for labour, appliances, or material. He +cannot check the expenditure of the Mining Manager, who may be a rogue +or a fool or both, for we have had samples of all sorts to our sorrow. +The Directors are in like case. Even where the information is honestly +supplied, they cannot judge whether the work is being properly carried +out or is costing a fair price, and the Mining Manager is left to his +own devices, with no one to check him nor any with whom he can consult +in specially difficult cases. Thus matters drift to the almost certain +conclusion of voluntary or compulsory winding up; and so many a +good property is ruined, and promising mines, which have never had a +reasonable trial, are condemned as worthless. But let us ask, would any +other business, even such as are less subject to unforeseen vicissitudes +than mining, succeed under similar circumstances? + +It is now very generally agreed that to the profitable development of +mining new countries, at all events, must look mainly for prosperity, +while other industries are growing. Therefore, we cannot too seriously +consider how we may soonest make our mines successful. + +What is the remedy for the unsatisfactory state of affairs we have +experienced? The answer is a more practical system of working from the +inception. Although it may evoke some difference of opinion I consider +it both justifiable and desirable that the State should take some +oversight of mining matters, at all events in the case of public +Companies. It would be a salutary rule that the promoters of any mining +undertaking should, before they are allowed to place it on the market, +obtain and pay for the services of a competent Government Mining +Inspector, who need not necessarily be a Government officer, but might, +like licensed surveyors, be granted a certificate of competency either +by a School of Mines or by some qualified Board of Examiners. The +certificate of such Inspector that the property was as represented, +should be given before the prospectus was issued. It is arguable whether +even further oversight might not be properly be taken by the State and +the report of a qualified officer be compulsory that the property was +reasonably worth the value placed upon it in the prospectus. + +Probably it will be contended that such restrictions would be an undue +interference with private rights, and the old aphorism about a fool and +his folly will be quoted. There are doubtless fools so infatuated +that if they were brayed in a ten hundred-weight stamp-battery the +"foolishness that had not departed from them" would give a highly +payable percentage to the ton. Yet the State in other matters tries by +numerous laws to protect such from their folly. A man may not sell a +load of wood without the certificate from a licensed weighbridge or a +loaf of bread without, if required, having to prove its weight; and we +send those to gaol who practise on the credulity and cupidity of fools +by means of the "confidence trick." Why not, therefore, where interests +which may be said to be national are involved, endeavour to ensure fair +dealing? + +Then with regard to the men who are to manage the mines, seeing that +a man may not become captain or mate of a river steamboat without some +certificate on competency, nor drive her engines before he has passed an +examination to prove his fitness, surely it is not too much to say that +the mine manager or engineer, to whose care are often confided the lives +of hundreds of men, and the expenditure of thousands of pounds, should +be required to obtain a recognised diploma to prove his qualifications. +The examinations might be made comparatively easy at first, but +afterwards, when by the establishment of Schools and Mines the +facilities have been afforded for men to thoroughly qualify, the +standard should be raised; and after a date to be fixed no man should be +permitted to assume the charge of a mine or become one of its officers +without a proper certificate of competency from some recognised School +of Mines or Technical College. The effect of such a regulation would in +a few years produce most beneficial results. + +In New Zealand, whose "progressive" legislature I do not generally +commend, they have, in the matter of mine management, at all events, +taken a step in the right direction. There a mine manager, before +he obtains his certificate, must have served at least two years +underground, and has to pass through a severe examination, lasting for +days, in all subjects relating to mining and machinery connected with +mining. In addition, he must prove his capacity by making an underground +survey, and then plotting his work. The examination is a stiff one, +as may be judged from the fact that between 1886 and 1891, only 27 +candidates passed. Then the conditions were made easier, and from that +date to 1895, 19 passed. Of the 46 students who gained first-class +honours, 30 have left for South Africa or Australia, in both of which +countries New Zealand certificated men are held in high estimation. + +But returning to the formation of the Company, care should be taken in +appointing Directors that at least one member of the Board is selected +on account of his special technical knowledge of mining, and others for +their special business capacity. The ornamental men with high sounding +names should not be required in legitimate ventures. Also, it is most +important that the business Manager or Secretary should be a specially +qualified man, who by experience has learned what are the requirements +of a mine doing a certain amount of work, so that a proper check may +be kept on the expenses. The more Companies such a Secretary has the +better, as one qualified man can supervise a large staff of clerks, who +would themselves be qualifying for similar work, and gaining a useful +and varied experience of mining business. An office of this description +having charge of a large number of mines is, in its way, a technical +school, and lads trained therein would be in demand as mine pursers, a +very responsible and necessary officer in a big mine. + +With respect to the men to whom the actual mining and treatment of ores +and machinery is committed the greatest mistakes of the past have been +that too much has been required from one man, a combination not to be +found probably in one man in a thousand. Such Admirable Crichtons are +rare in any profession or business, and that of mining is no exception. +Men who profess too much are to be distrusted. Your best men are they +who concentrate their energies and intellects in special directions. +The Mining Manager should, if possible, be chosen from men holding +certificates of competency from some technical mining school and, +of course, should, in addition, have some practical experience, not +necessarily as Head Manager. He should understand practical mine +surveying and calculation of quantities, be able to dial and plot out +his workings, and prepare an intelligible plan thereof for the use of +the Directors, and should understand sufficient of physics, particularly +pneumatics and hydraulics, to ensure thoroughly efficient pumping +operations without loss of power from unnecessarily heavy appliances. +Any other scientific knowledge applicable to his business which he may +have acquired will tell in his favour, but he must, above all things, +be a thoroughly practical man. Such men will in time be more readily +procurable, as boys who have passed through the various Schools of Mines +will be sent to learn their business practically at the mines just as we +now, having given a lad a course of naval instruction, send him to sea +to learn the practical part of his life's work. + +But, of course, more is wanted on a mine than a man who can direct the +sinking of shafts, driving of levels, and stoping of the lode. Much +loss and disappointment have resulted in the past from unsuitable, +ineffective, or badly designed and erected machinery, whether for +working the mine or treating the ores. To obviate this defect a +first-class mining engineer is required. + +Then, also, day by day we are more surely learning that mining in all +its branches is a science, and that the treatment of ores and extraction +of the metals is daily becoming more and more the work of the laboratory +rather than of the rule-of-thumb procedure of the past. Every mine, +whether it be of gold, silver, tin, copper, or other metal, requires the +supervision of a thoroughly qualified metallurgist and chemist, and one +who is conversant with the newest processes for the extraction of the +metals from their ores and matrices. + +It has then been stated that to ensure effective working each mine +requires, in addition to competent directors, a business manager, +mining-manager, and assistants, engineer, chemist, and metallurgist, +with assistant assayers, etc., all highly qualified men. But it will be +asked, how are many struggling mines in sparsely populated countries +to obtain the services of all these eminent scientists? The reply is by +co-operation. One of the most ruinous mistakes of the past has been that +each little mining venture has started on an independent course, with +different management, separate machinery, etc. Can it then be wondered +at that our gold-mining is not always successful? + +Under a co-operative system all that each individual mine would require +would be a qualified, practical miner capable of opening and securing +the ground in a miner-like manner, and a good working engineer; and +in gold-mining, where the gold is free in its matrix, a professional +amalgamator, or lixiviator. For the rest, half a dozen or more mines may +collectively retain the services of a mine manager of high attainments +as general inspector and superintendent, and the same system could be +adopted with respect to an advising metallurgist and an engineer. For +gold, as indeed for other metals, a central extracting works, where the +ores could be scientifically treated in quantity, might be erected at +joint cost, or might easily be arranged for as a separate business. + +A very fruitful cause of failure is the fatuous tendency of directors +and mine managers to adopt new processes and inventions simply because +they are new. As an inventor in a small way myself, and one who is +always on the watch for improved methods, I do not wish to discourage +intelligent progress; but the greatest care should be exercised by those +having the control of the money of shareholders in mining properties +before adopting any new machinery or process. + +We have seen, and unfortunately shall see, many a promising mining +company brought to grief by this popular error. The directors of mining +companies might, to use an American saying, "paste this in their hats" +as a useful and safe aphorism. "LET OTHERS DO THE EXPERIMENTING; WE ARE +WILLING TO PAY ONLY FOR PROVED IMPROVEMENTS." I can cordially endorse +every word of the following extracts from Messrs. McDermott and +Duffield's admirable little work, "Losses in Gold Amalgamation." + +"Some directors of mining companies are naturally inclined to listen to +the specious promises of inventors of novel processes and new machinery, +forgetting their own personal disadvantage in any argument on +such matters, and assuming a confidence in the logic of their own +conclusions, while they ignore the fruitful experience of thousands +of practical men who are engaged in the mining business. The repeated +failures of directors in sending out new machinery to their mines ought +by this time to be a sufficient warning against increasing risks that +are at once natural and unavoidable, and to deter them from plunging +their shareholders into experiments which, in ninety-nine cases out of a +hundred, result in nothing but excessive and needless expenses. + +"It is certain that new machines and new processes are, and will be, +given attention by mining men in proportion to their probable merits; +but the proper place for experiments is in a mill already as successful +as under known processes it can be made. In a new enterprise, even when +the expense of an experiment is undertaken by the inventor, the loss to +the mine-owner in case of failure must be very great, both in time +and general running expenses. Directors should not believe that a +willingness to risk cash in proving an invention is necessarily any +proof of value of the same; it is only a measure of the faith of the +inventor, which is hardly a safe standard to risk shareholders' money +by. + +"The variety of modifications in approved processes ought at least to +suggest the desirability of exhausting the known, before drawing on the +unknown and purely speculative. It should also be borne in mind that +what might appear at first sight to be new processes, and even new +machinery, are, in fact, often nothing but old contrivances and +plausible theories long ago exploded among practical men. + +"Many mining companies have been ruined, without any reference to their +mines, through men deciding on the reasonableness of new process and +machinery who have no knowledge of the business in hand. It is assumed +often, that if an inventor or manufacturer of new machinery will agree +to guarantee success, or take no pay if not successful, the company +takes no risk. In actual fact a whole year is wasted in most cases, +failure spoils the reputation of the company, running expenses have +continued, and further working capital cannot be raised, because +all concerned have lost confidence by the failure to obtain returns +promised. All this in addition to the regular, unavoidable risks of +mining itself, which may, at any moment during the year lost, call +for increased expenses and increased faith in ultimate success. To the +mining man who makes money by the business, the natural risks of mining +is all he will take; it is sufficient; and when he invests more money in +machinery he takes good care that he takes no chances of either failure +or delay. + +"The following are rules which no mining company or individual +mine-owner can afford to neglect. + +"(1) The risk should be confined to mining. No body of directors is +justified in taking a shareholder's money and investing it in new +processes or machinery when the subscription was simply for a mining +venture. Directors are invariably incapable of deciding whether a +so-called improvement in machinery or process is really so or not, and +the reasonable course is to follow established precedents. + +"(2) The risk of selecting an incompetent manager should be reduced to +minimum by taking a man with a successful record in the particular work +to be done. The manager selected should be prohibited, as much as the +directors, from experimenting with new methods or machinery. A really +experienced man will require no check in this direction, as he will not +risk ruining his reputation. + +"(3) The only time for a company to experiment is when the mine is +paying well by the usual methods, and the treasury is in a condition to +speculate a little in possible improvements without jeopardising regular +returns." + +Probably this is the best place to insert another word of warning to +directors who are not mining specialists, and also to investors in gold +mining shares. Assays of auriferous lode material are almost invariably +worthless as a guide in the real value of the stone in quantity. The one +way to decide this is by battery treatment in bulk, and then only after +many tons have been put through. The reason is obvious. First, the +prospector or company promoter, if he knows it, is not in the least +likely to pick the worst piece of stone in the heap for assay; and, +secondly, even should the sample be selected with the sole object of +getting a fair result, no living man can judge the value of a gold lode +by the result of treatment of an ounce of stone. So when you see it +stated that Messrs. Oro and Gildenstein, the celebrated assayers, have +found that a sample of rock from the Golden Mint Mine, Golconda, assays +at the rate of 2,546 oz. 13 dwt. and 21 gr. to the ton, and that there +are thousands of tons of similar stone in sight, the statement should +be received with due caution. The assay is doubtless correct, but the +deductions therefrom are most misleading. + +A few words of advice also to directors of mine-purchasing companies and +syndicates, of which there are now so many in existence, may probably be +found of value. It is not good policy as a general rule to buy entirely +undeveloped properties, unless such have been inspected by your own man, +who is both competent and trustworthy, and who should have indeed an +interest in the profits. Large areas, although so popular in England, +do not compensate for large bodies of payable ore; the most remunerative +mine is generally one of comparatively small area, but containing a +large lode formation of payable but often low grade, ore. + +It is worse still, of course, to buy a practically worked out mine, +though this too is sometimes done. It must be remembered that mining, +though often so profitable, is nevertheless a destructive industry, thus +differing from agriculture, which is productive, and manufactures, which +are constructive. Every ton of stone broken and treated from even the +best gold mine in the world makes that mine the poorer by one ton of +valuable material; thus, to buy a mining property on its past reputation +for productiveness is, as a rule, questionable policy, unless you know +there is sufficient good ore in sight to cover the purchase cost and +leave a profit. + +One of the greatest causes of non-success of gold-mining ventures, +particularly when worked by public companies, is the lack of actual +personal supervision, and hence, among other troubles, is that +ultra-objectionable one--gold stealing from the mills, or, in alluvial +mining, from the tail races. As to the former, the following appeared +in 1893 in the London _Mining Journal_, and is, I think, worthy of the +close consideration of mine directors in all parts of the world:-- + +"No one that has not experienced the evil of gold thieving from +reduction mills can have any idea of the pernicious element it is, and +the difficulty, once that it has got 'well hold,' of rooting it out. +It permeates every class of society in the district connected with the +industry, and managers, amalgamators, assayers, accountants, aye, even +bank officials, are 'all on the job' to 'get a bit' while there is an +opportunity. To exterminate the hateful monster requires on the part +of the mine proprietors combined, stern and drastic measures undertaken +under the personal supervision of one or more of their directors, and +in many instances necessitating the removal of the whole of the official +staff." + +The writer narrates how about twenty years ago he was led to suspect +that in an Australian mine running forty head of stamps, in which he +held a controlling interest, the owners were being defrauded of about a +fourth of the gold really contained in the ore, and the successful steps +taken to check the robbery. + +"We first of all dispensed with the services of the general manager, and +then issued the following instructions to the mine and mill managers, +I remaining at the mine to see them carried out until I substituted a +practical local man as agent, who afterwards carried on the work most +efficiently:-- + +"(a) Both of these officials to keep separate books and accounts; in +other words, to be distinct departments. + +"(b) The ore formerly was all thrown together and put through the mill. +I subdivided it into four classes, A, B, C, and D, representing deep +levels north and upper levels north, deep levels south and upper levels +south, and allotted to each class ten heads of stamps at the mill. + +"(c) The mine manager to try three prospects, forenoon and afternoon +of each day, from the dumps of each of the four classes and record in a +book to be kept for that purpose the estimated mill yield of each one. + +"(d) The mill manager was required to do the same at the mill and keep +his record. + +"(e) There were four underground bosses in each shift, twelve in all. +I had a book fixed at the top of the shaft in which I required each of +these men, at the expiry of every shift, to record any change in the +faces of the quartz and particularly in regard to quality. + +"(f) Having divided the ore into four classes I instructed the +amalgamators, of which there were two in each shift, six in all, that I +required the amalgam from each to be kept separate, with the object of +ascertaining what each part of the mine produced. + +"(g) I procured padlocks for the covering boards of the mercury tables +and gave the keys to the amalgamators with instructions that they were +not to hand them over to any one except the exchange shift without my +written authority, and instructed them that they should clean down the +plates every three hours, and after cleaning down the amalgam, buckets +to be placed in the cleaning room, which I instructed to be kept locked +and the key in charge of the watchman night and day. + +"(h) The whole of the amalgam taken from the plates during each +twenty-four hours to be cleaned and squeezed by the two amalgamators on +duty every forenoon at nine o'clock in the presence of the mill manager, +who should weigh each lot and enter it in a book to be kept for the +purpose, and the entry to be signed by the mill manager and both +amalgamators as witnesses. + +"(i) Every alternate Friday the mortars (boxes) to be cleaned out; the +work to be commenced punctually at eight A.M. by the six amalgamators in +the presence of the mill manager, assisted by the three amalgam cleaning +room watchmen and the four battery feeders on duty, prohibiting any of +them from leaving until the cleaning up was finished, and the amalgam +cleaned, squeezed and weighed, and the amount entered by the mill +manager in the record look and attested by the amalgamators. + +"I think the intelligent readers (particularly those with a knowledge +of the business) will see the drift of the above regulations, viz., for +there to be any peculation the whole of the battery staff--fourteen in +all--would have to participate in it, and the number was too many to +keep a secret. Formerly the amalgam cleaning room was sacred to the mill +manager, and on announcing to that official the new instructions he at +once tendered his resignation in a tone of offended dignity, immediately +followed by that of the mine manager. It is a significant fact that +shortly afterwards these two officials purchased a large mill and other +property at a cost of ten thousand pounds, and that the mine yielded +for the following three years during which I was connected with it an +average of over 17 dwt. to the ton, as against formerly 10 to 12 dwt. + +"The reader must draw his own conclusions. I used to make it a practice +to visit the mine daily and prospect the ore, and having the mine and +mill managers' daily prospecting as a guide as well as my own, every +man at the mill knew it was impossible for them to thieve without my +detecting it; moreover, I made it a rule to discharge any of the mill +employees that I discovered were interested in any small private claims. + +"The crux of the whole thing is having a practical miner at the head of +affairs, and it is impossible for him to thieve if the work is carried +out in the manner I have described." + +To bring the whole matter to a conclusion. It may be taken as a safe +axiom that to make gold mining in the mine as distinct from mining on +the Stock Exchange really profitable the same system of economy, of +practical supervision, and scientific knowledge which is now adopted in +all other businesses must be applied to the raising and extraction of +the metal. Then, and not till then, will genuine mining take the place +to which it is entitled amongst our industries. + + + +CHAPTER XI + +RULES OF THUMB + +This chapter has been headed as above because a number of the rules +and recipes given are simply practical expedients, not too closely +scientific. My endeavour has been to supply practical and useful +information in language as free from technicalities as possible, so as +to adapt it to the ordinary miner, mill operator and prospector, many +of whom have had no scientific training. Some of the expedients are +original devices educed by what we are told is the mother of inventions; +others are hints given by practical old prospectors who had met with +difficulties which would be the despair of a man brought up within reach +of forge, foundry, machine shop, or tradesmen generally. There are many +highly ingenious and useful contrivances besides these I have given. + +LIVING PLACES + +The health of the prospector, especially in a new country, depends +largely on his housing--in which particular many men are foolishly +careless, for although they are aware that they will be camped out for +long periods, yet all the shelter they rely on is a miserable calico +tent, often without a "fly," while in some cases they sometimes even +sleep on the wet, or dusty, ground. Such persons fully deserve the ill +health which sooner or later overtakes them. A little forethought and +very moderate ingenuity would render their camp comparatively healthy +and comfortable. + +In summer the tent is the hottest, and in winter the coldest of +domiciles. The "pizie" or "adobie" hut, or, where practicable, the +"dugout," are much to be preferred, especially the latter. "Pizie" or +"adobie" is simply surface soil kneaded with water and either moulded +between boards like concrete, to construct the walls, or made into large +sun-dried bricks. Salt water should not be used, as it causes the wall +to be affected by every change of weather. A properly constructed house +of this material, where the walls are protected by overhanging eaves, +are practically everlasting, and the former have been standing for +centuries. There are buildings of pizie or adobie in Mexico, California +and Australia which are as good as new, although the latter were built +nearly a century ago. + +Adobie dwellings are warm in winter and cool in summer, and can be kept +clean and healthy by occasional coatings of lime whitewash. + +The dugout is even more simple in construction. A cutting, say ten feet +wide, is put into the base of a hill for say twelve feet until the back +wall is, say, ten feet high, the sides starting from nothing to that +height. The front and such portion as is required of the side walls are +next constructed of pizie or rough stone, with mud mortar, and the roof +either gabled or skillion of bough, grass, or reed thatch, and covered +with pizie, over which is sometimes put another thin layer of thatch to +prevent the pizie being washed away by heavy rain. Nothing can be more +snug and comfortable than such a house, unless the cows, as Mark Twain +narrates, make things "monotonous" by persistently tumbling down the +chimney. + +When the Burra copper mines were in full work in Australia, the banks of +the Burra Creek were honeycombed like a rabbit warren with the "dugout +homes" of the Cornish miners. The ruins of these old dugouts now extend +for miles, and look something like an uncovered Pompeii. + +When water is scarce and the tent has to be retained, much can be done +to make the camp snug. I occupied a very comfortable camp once, of which +my then partner, a Dane, was the architect. We called it "The Bungalow," +and it was constructed as follows: First we set up our tent, 10 ft. by +8 ft., formed of calico, but lined with green baize, and covered with a +well set fly. + +Next we put in four substantial forked posts about 10 ft. high and 15 +ft. apart, with securely fixed cross pieces, and on the top was laid a +rough flat roof of brush thatch; the sides were then treated in the same +way, but not so thickly, being merely intended as a breakwind. + +The tent with its two comfortable bunks was placed a little to one side, +the remaining space being used as a dining and sitting room all through +the summer. Except in occasional seasons of heavy rain, when we were +saved the trouble of washing our dishes, the tent was only used for +sleeping purposes, and as a storehouse for clothes and perishable +provisions. I have "dwelt in marble halls" since then, but never was +food sweeter or sleep sounder than in the old bush bungalow. + +A BUSH BED + +To make a comfortable bush bedplace, take four forked posts about 3 ft. +6 in. long and 2 to 3 in. in diameter at the top; mark out your bedplace +accurately and put a post at each corner, about 1 ft. in the ground. +Take two poles about 7 ft. long, and having procured two strong +five-bushel corn sacks, cut holes in the bottom corners, put the poles +through, bringing the mouths of the sacks together, and secure them +there with a strong stitch or two. Put your poles on the upright forked +sticks, and you have a couch that even Sancho Panza would have envied. +It is as well to fix stretchers or cross stays between the posts at head +and foot. + +In malarial countries, sleeping on the ground is distinctly dangerous, +and as such districts are usually thickly timbered, the Northern +Territory hammock is an admirable device, more particularly where +mosquitoes abound. + +NORTHERN TERRITORY HAMMOCK + +This hammock, which is almost a standing bedplace when rigged, is +constructed as follows:--To a piece of strong canvas 7 feet long and 2 +1/2 feet wide, put a broad hem, say 3 1/2 inches wide at each end. Into +this hem run a rough stick, about 2 feet 8 inches by 2 inches diameter. +Round the centre of the stick pass a piece of strong three-quarter inch +rope, 8 to 10 feet long and knot it, so as to leave a short end in +which a metal eye is inserted. To each end of the two sticks a piece of +quarter-inch lashing, about 6 feet long, is securely attached. + +To make the mosquito covering take 18 feet of ordinary strong cheese +cloth, and two pieces of strong calico of the same size as the canvas +bed; put hems in the ends of the upper one large enough to take +half-inch sticks, to all four extremities of which 8 feet of whipcord is +to be attached. The calico forms the top and bottom of what we used to +call the "meat safe," the sides being of cheese cloth. A small, flapped +opening is left on the lower side. When once inside you are quite safe +from mosquito bites. + +To rig the above, two trees are chosen 7 to 8 feet apart, or two stayed +poles can be erected if no trees are available. The bed is rigged about +3 feet from the ground by taking the rope round the trees or poles, and +pulling the canvas taut by means of the metal eyelet. Then the lashings +at the extremities of the sticks are fixed about 3 feet further up the +trees and you have a bed something between a hammock and a standing bed. +The mosquito net is fixed above the hammock in a similar manner, except +that it does not require the centre stay. + +An old friend of mine once had a rather startling experience which +caused him to swear by the Northern Territory hammock. He was camped +near the banks of a muddy creek on the Daly River, and had fortunately +hung his "meat safe" about four feet high. The night was very dark, and +some hours after retiring he heard a crash among his tin camp utensils, +and the noise of some animal moving below him. Thinking his visitor was +a stray "dingo," or wild dog, he gave a yell to frighten the brute away, +and hearing it go, he calmly went to sleep again. Had he known who his +caller really was, he would not have felt so comfortable. In the +morning on the damp ground below, he found the tracks of a fourteen foot +alligator, which was also out prospecting, but which, fortunately, had +not thought of investigating the "meat safe." + +PURIFYING WATER + +There is not a more fertile disease distributor, particularly in a new +country, than water. The uninitiated generally take it for granted that +so long as water looks clear it is necessarily pure and wholesome; as +a matter of fact the contrary is more usually the case, except in very +well watered countries, and such, as a rule, are not those in which gold +is most plentifully got by the average prospector. I have seen foolish +fellows, who were parched with a long tramp, drink water in quantity in +which living organisms could be seen with the naked eye, without taking +even the ordinary precaution of straining it through a piece of linen. +If they contracted hydatids, typhoid fever, or other ailments, which +thin our mining camps of the strong, lusty, careless youths, who could +wonder? + +The best of all means of purifying water from organic substances is to +boil it. If it be very bad, add carbon in the form of the charcoal from +your camp fire. If it be thick, you may, with advantage, add a little of +the ash also. + +I once rode forty-five miles with nearly beaten horses to a native +well, or rock hole, to find water, the next stage being over fifty miles +further. The well was found, but the water in it was very bad; for in +it was the body of a dead kangaroo which had apparently been there for +weeks. The wretched horses, half frantic with thirst, did manage to +drink a few mouthfuls, but we could not. I filled our largest billycan, +holding about a gallon, slung it over the fire and added, as the wood +burnt down, charcoal, till the top was covered to a depth of two +inches. With the charcoal there was, of course, a little ash containing +bi-carbonate of potassium. The effect was marvellous. So soon as the +horrible soup came to the boil, the impurities coagulated, and after +keeping it at boiling temperature for about half an hour, it was removed +from the fire, the cinders skimmed out, and the water allowed to settle, +which it did very quickly. It was then decanted off into an ordinary +prospector's pan, and some used to make tea (the flavour of which can be +better imagined than described); the remainder was allowed to stand +all night, a few pieces of charcoal being added. In the morning it was +bright, clear, and absolutely sweet. This experience is worth knowing +as many a bad attack of typhoid and other fevers would be averted if +practical precautions of this kind were only used. + +TO OBTAIN WATER FROM ROOTS + +The greatest necessity of animal life is water. There are, however, +vast areas of the earth's surface where this most precious element is +lamentably lacking, and such, unfortunately, is the case in many rich +auriferous districts. + +To the practical man there are many indications of water. These, of +course, vary in different countries. Sometimes it is the herbage, but +probably, the best of all is the presence of carnivorous animals and +birds. These are never found far from water. In Australia the not +over-loved wily old crow is a pretty sure indicator of water within +reasonable distance--water may be extracted from the roots of the Mallee +(_Eucalyptus dumosa_ and _gracilis_)--the Box (_Eucalyptus hemiphloia_) +and the Water Bush (_Hakea leucoptera_). To extract it the roots are dug +up, cut into lengths of about a foot, and placed upright in a can; the +lower ends being a few inches above the bottom. It is simply astonishing +how much wholesome, if at times somewhat astringent, water may thus be +obtained in a few hours, particularly at night. + +_Hakea leucoptera_. "Pins and needles."--Maiden, in his work "Useful +Native Plants of Australia," says: "In an experiment on a water-yielding +_Hakea_, the first root, about half an inch in diameter and six or eight +feet long, yielded quickly, and in large drops about a wine-glass full +of really excellent water." + +This valuable, though not particularly ornamental shrub (for it never +attains to the dimensions of a tree), is found, to the best of my +belief, in all parts of Australia, although it is said to be absent from +West Australia. As to this I don't feel quite sure. I have seen it "from +the centre of the sea" as far west as Streaky Bay, and believe I have +seen it further West still. Considering the great similarity of much of +the flora of South Africa to that of Australia, it is probable that +some species of the water-bearing _Hakea_ might be found there. It can +readily be recognised by its acicular, needle-like leaves, and more +particularly by its peculiarly shaped seed vessel, which resembles the +pattern on an old-fashioned Indian shawl. + +If the water found is too impure for drinking purposes and the +trouble arises from visible animalculae only, straining through a +pocket-handkerchief is better than nothing; the carbon filter is better +still; but nothing is so effective as boiling. A carbon filter is a tube +with a wad of compressed carbon inserted, through which the water is +sucked, but as a rule clay-coloured water is comparatively innocuous, +but beware of the bright, limpid water of long stagnant rock +water-holes. + +TO MAKE AN EFFECTIVE FILTER + +Take a nail-can, keg, cask, or any other vessel, or even an ordinary +wooden case (well tarred inside, if possible, to make it water-tight). +Make a hole or several holes in the bottom, and set it over a tank or +bucket. Into the bottom of the filter put (1) a few inches of washed +broken stone; (2) about four inches of charcoal; (3) say three inches +of clean coarse sand (if not to hand you can manufacture it by crushing +quartz with your pestle and mortar), and (4) alternate layers of +charcoal and sand until the vessel is half filled. Fill the top half +with water, and renew from time to time, and you have a filter which is +as effective as the best London made article. _But it is better to boil +your water whether you filter afterwards or not._ + +Clear the inside of the water-cask frequently, and occasionally add +to the water a little Condy's fluid, as it destroys organic matter. A +useful cement for stopping leaky places in casks is made as follows: +Tallow 25 parts, lard 40 parts, sifted wood ash 25 parts. Mix together +by heating, and apply with a knife blade which has just been heated. + +CANVAS WATER BAGS + +Are easily made, and are very handy for carrying small supplies +of drinking-water when prospecting in a dry country; they have the +advantage of keeping the water cool in the hottest weather, by reason on +the evaporation. The mouthpiece is made of the neck of a bottle securely +sewn in. + +MEDICINE CASE + +Medicine is also a matter well worthy of thought. The author's worst +enemy would not call him a mollycoddle, yet he has never travelled in +far wilds without carrying something in the way of medicine. First, +then, on this subject, it cannot be too often reiterated that if common +Epsom salts were a guinea an ounce instead of a penny the medicine +would be valued accordingly, but it is somewhat bulky. What I especially +recommend, however, is a small pocket-case of the more commonly known +homeopathic remedies, "Mother tinctures," which are small, light, and +portable, with a small simple book of instructions. Though generally +an allopath in practice, I once saved my own life, and have certainly +helped others by a little knowledge in diagnosing complaints and having +simple homeopathic remedies at hand to be used in the first stages of +what might otherwise have been serious illnesses. + +PRODUCING FIRE + +Every one has heard, and most believe, that fire may be easily produced +by rubbing together two pieces of wood. I have seen it done by natives, +but they seldom make use of the operation, which is generally laborious, +preferring to carry lighted fire sticks for miles. I have never +succeeded in the experiment. + +Sometimes, however, it is almost a matter of life or death to be able to +produce fire. The back of a pocket knife, or an old file with a fragment +of flint, quartz, or pyrites struck smartly together over the remains of +a burnt piece of calico, will in deft hands produce a spark which can be +fanned to a glow, and so ignite other material, till a fire is produced. + +Also it may not be generally known that he who carries a watch carries +a "burning glass" with which he can, in clear weather, produce fire +at will. All that is required is to remove the glass of your watch and +carefully three parts fill it with water (salt or fresh). This forms +a lens which, held steadily, will easily ignite any light, dry, +inflammable substance. + +When firearms are carried, cut a cartridge so that only about a quarter +of the charge of powder remains. Damp some powder and rub it on a small +piece of dry cotton cloth or well-rubbed brown paper. Push a loose +pellet of this into the barrel, insert your half cartridge, fire at the +ground, when the wad will readily ignite, and can be blown into flame. + +TO COPY CORRESPONDENCE + +The prospector is not usually a business man; hence in dealing with +business men who, like Hamlet, are "indifferent honest," he frequently +comes to grief through not having a copy of his correspondence. It is +most desirable, therefore, either to carry a carbon paper duplicating +book and a stylus, or by adding a little sugar to good ordinary black +ink you may make a copying ink; then with the aid of a "yellow back" +octavo novel, two pieces of board, and some ordinary tissue paper, you +may take a copy of any letter you send. + +TO PROVIDE A SIMPLE TELEGRAPHIC CODE + +Buy a couple of cheap small dictionaries of the same edition, send one +to your correspondent with an intimation that he is to read up or down +so many words from the one indicated when receiving a message. Thus, +if I want to say "Claim is looking well," I take a shilling dictionary, +send a copy to my correspondent with the intimation that the real word +is seven down, and telegraph--"Civilian looking weird;" this, if looked +up in Worcester's little pocket dictionary, for instance, will read +"Claim looking well." Any dictionary will do, so long as both parties +have a copy and understand which is the right word. By arrangement this +plan can be varied from time to time if you have any idea that your code +can be read by others. + +A SERVICEABLE SOAP + +Wood ashes from the camp fire are boiled from day to day in a small +quantity of water, and allowed to settle, the clear liquid being +decanted off. When the required quantity of weak lye has been +accumulated, evaporate by boiling, till a sufficient degree of strength +has been obtained. Now melt down some mutton fat, and, while hot, add to +the boiling lye. Continue boiling and stirring till the mixture is about +the consistency of thick porridge, pour into any convenient flat vessel, +and let it stand till cool. If you have any resin in store, a little +powdered and added gradually to the melting tallow, before mixing with +the lye, will stiffen your soap. + +TO CROSS A FLOODED STREAM + +Take a half-gallon, or larger, tin "billy can," enclose it in a strong +cotton handkerchief or cotton cloth, knotting same over the lid, invert, +and, taking the knot in the hand, you have a floating appliance which +will sustain you in any water, whether you are a swimmer or not. The +high silk hat of civilisation would act as well as the can, but these +are not usually found far afield. + +TO MAKE A HIDE BUCKET + +At times when prospecting in an "incline" or "underlay" shaft, +particularly where the walls of the lode are irregular, a hide bucket +will be found preferable to an iron one. The mode of manufacture is as +follows: Procure an ox hide, "green," if possible; if dry, it should +be soaked until quite soft. Cut some thin strips of hide for sewing or +lacing. Now shape a bag or pocket of size sufficient to hold about +a hundredweight of stone, and by puncturing the edges with a knife, +marline-spike, or other pointed tool, sew together; make a handle of +twisted or pleated hide, and having filled your bucket with dry sand or +earth let it stand till the whole is quite dry, when it will be properly +distended and will maintain its shape until worn out. + +TO MAKE A "SLUSH LAMP" + +Where candles are scarce and kerosine is not, a "slush lamp" is a useful +substitute. Take an old but sound quart tin pannikin, half fill it with +sand or earth, and prepare a thin stick of pine, round which wrap a +strip of soft cotton cloth. The stick should be about half an inch +longer than the depth of the pannikin. Melt some waste fat, fill the +pannikin therewith, push the stick down into the earth at the +bottom, and you have a light, which, if not equal to the electric or +incandescent gas burner, is quite serviceable. In Australia the soft +velvety core of the "bottle brush," _Banksia marginata_, is often used +instead of the cotton wick. + + + +CHAPTER XII + +RULES OF THUMB + +MINING APPLIANCES AND METHODS + +A TEMPORARY FORGE + +What prospector has not at times been troubled for the want of a forge? +To steel or harden a pick or sharpen a drill is comparatively easy, +but there is often a difficulty in getting a forge. Big single action +bellows are sometimes bought at great expense, and some ingenious +fellows have made an imitation of the blacksmith's bellows by means of +sheepskins and rough boards. + +With inadequate material and appliances to hand, the following will +be found easier to construct and more lasting when constructed. Only +a single piece of iron is required, and, at a pinch, one could even +dispense with that by using a slab of talcose material, roughly shaping +a hearth therein and making a hole for the blast. First, construct a +framing about the height of an ordinary smith's forge. This can made +with saplings and bark, or better still, if available, out of an empty +packing case about three feet square. Fill the frame or case with +slightly damped earth and ram it tight, leaving the usual hollow hearth. +Then form a chamber below the perforated hearth opening to the rear. +Now construct a centrifugal fan, such as is used for the ventilation of +shallow shafts and workings. Set this up behind the hearth and revolve +by means of a wooden multiplying wheel. A piece of ordinary washing line +rope, or sash line rope, well resined if resin can be got--but pitch, +tar, or wax will do by adding a little fine dust to prevent sticking--is +used as a belt. With very rough materials a handy man can thus make a +forge that will answer ordinary requirements.--N.B. Do not use clay for +your hearth bed unless you can get a highly aluminous clay, and can give +it full time to dry before the forge fire is lit. Ordinary surface soil, +not too sandy, acts well, if damped and rammed thoroughly. Of course, +if you can get an iron nozzle for your blower the whole operation is +simplified. + +SIMPLE WAY OF MAKING CHARCOAL + +Dig a pit 5 feet square by 3 feet deep and fill with fuel. After +lighting, see that the pit is kept full. The hot embers will gradually +sink to the bottom. The fuel should be kept burning fiercely until the +pit seems almost full, when more fuel should be added, raising the heap +about a foot above the level of the ground. The earth dug out of the pit +should then be shovelled back over the burning mass. After leaving it to +cool for 24 hours the pit will be found nearly full of charcoal. About +one-quarter the weight of the dry fuel used should be recovered in +charcoal. + +ROUGH SMELTING ON THE MINE + +Rough smelting on the mine is effected with a flux of borax, carbonate +of soda, or, as I have often done, with some powdered white glass. When +the gold is smelted and the flux has settled down quietly in a liquid +state, the bulk of the latter may be removed, to facilitate pouring into +the mould, by dipping an iron rod alternately into the flux and then +into a little water, and knocking off the ball of congealed flux which +adheres after each dip. This flux should, however, be crushed with a +pestle and mortar and panned off, as, in certain cases, it may contain +tiny globules of gold. + +MISFIRES IN BLASTING + +One of the most common sources of accident in mining operations is due +either to carelessness or to the use of defective material in blasting. +A shot misses, generally for one of two reasons; either the explosive, +the cap, or the fuse (most often the latter), is inferior or defective; +or the charging is incompletely performed. Sometimes the fuse is not +placed properly in the detonator, or the detonator is not properly +enclosed in the cartridge, or the fuse is injured by improper tamping. +If several shots have been fired together, particularly at the change +of a "shift," the men who have to remove the broken material may in so +doing explode the missed charge. Or, more inexcusable still, men will +often be so foolish as to try to clear out the drill hole and remove +the missed cartridge. When a charge is known to have missed all that +is necessary to do in order to discharge it safely is to remove a few +inches of "tamping" from the top of the drill hole, place in the bore +a plug of dynamite with cap and fuse attached, put an inch or two of +tamping over it and fire, when the missed charge will also be exploded. +Of course, judgment must be used and the depth of the drill taken into +consideration. As a rule, miners use far more tamping than is at all +requisite. The action of the charge will generally be found quite as +effective with a few inches of covering matter as with a foot or more, +while the exploding of misfire cartridges is rendered simple, as no +removal of tamping is required before placing the top "plug" in case of +misfire. + +TO PREVENT LOSS OF RICH SPECIMENS IN BLASTING + +When blasting the cap of a lode, particularly on rich shutes of gold, +the rock is apt to fly, and rich specimens may be thrown far afield and +so be lost. A simple way of avoiding this is to procure a quantity +of boughs, which tie into loose bundles, placing the leafy parts +alternately end for end. Before firing, pile these bundles over the +blast and, if care is used, very few stones will fly. The same device +may be used in wide shallow shafts. + +A SIMPLE MODE OF RETORTING SMALL QUANTITIES OF AMALGAM + +Clean your amalgam and squeeze it as hard as possible through strong +calico or chamois leather. Take a large sound potato, cut off about a +quarter from one end and scoop out a hole in the centre about twice as +big as the ball of amalgam. Procure a piece of flat iron--an old spade +will do as well as anything--insert the amalgam, and, having placed the +potato, cut side downwards, thereon, put the plate of iron on the forge, +heat up first gently, then stronger, till separation has taken place, +when the gold will be found in a bright clean button on the plate +and the mercury in fine globules in the potato, from which it can be +re-collected by breaking up the partly or wholly cooked tuber under +water in an enamelled or ordinary crockery basin. + +TO RETORT SMALL QUANTITIES OF MERCURY FOR AMALGAMATING ASSAY TESTS + +Get two new tobacco pipes similar in shape, with the biggest bowls and +longest stems procurable. Break off the stem of one close to the bowl +and fill the hole with well worked clay (some battery slimes make the +best luting clay). Set the stemless pipe on end in a clay bed, and fill +with amalgam, pass a bit of thin iron or copper wire beneath it, +and bend the ends of the wire upwards. Now fit the whole pipe, bowl +inverted, on to the under one, luting the edges of both well with clay. +Twist the wire over the top with a pair of nippers till the two bowls +are fitted closely together, and you have a retort that will stand any +heat necessary to thoroughly distil mercury. + +A SIMPLE MODE OF ASCERTAINING THE NOMINAL HORSE-POWER OF AN ENGINE + +Multiply the internal diameter of the cylinder by itself and strike off +the last figure of the quotient. The diameter is + + 20" X 20" + 20 + ____ + 400. The H.P. is 40. + +The following rules will be found more professionally accurate from +an engineering standpoint, though the term "horse-power" is not now +generally employed. + +_To find the Nominal Horse-power_.--For _non-condensing_ engines: +Multiply the square of the diameter of the cylinder in inches by 7 and +divide the product by 80. For _condensing_ engines: Multiply the square +of the diameter of the cylinder in inches by 7 and divide the product by +200. + +_To find the Actual Horse-power_ of an engine, multiply the area of the +cylinder in square inches by the average effective pressure in pounds +per square inch, less 3 lb. per square inch as the frictional allowance, +and also by the speed of the piston in feet per minute, dividing the +product by 33,000, and the quotient will be the actual horse-power. + +"SCALING" COPPER PLATES + +To "scale" copper plates they may be put over a charcoal or coke fire +to slowly sublimate the quicksilver. Where possible, the fireplace of +a spare boiler can be utilised, using a thin red fire. After the entire +evaporation of the quicksilver the plates should be slowly cooled, +rubbed with hydrochloric acid, and put in a damp place overnight, then +rubbed with a solution of sal ammoniac and nitre in equal parts, and +again heated slowly over a red fire. They must not be allowed to get red +hot; the proper degree of heat is indicated by the gold scale rising +in blisters, when the plates should be taken from the fire and the gold +scraped off. Any part of the plate on which the gold has not blistered +should be again rubbed with the solution and fired. The gold scale +should be collected in a glass or earthen dish and covered with nitric +acid, till all the copper is dissolved, when the gold can be smelted in +the usual way; but after it is melted corrosive sublimate should be put +in the crucible till a blue flame ceases to be given off. + +_A Second Method_ + +The simplest plan I know is to have a hole dug nine inches deep by about +the size of the plate to be scaled; place a brick at each corner, and +on each side, halfway between, get up a good fire; let it burn down to +strong embers, or use charcoal, then place the plate on three bars of +iron extending between the three pairs of bricks, have a strong solution +of borax ready in which soak strips of old "table blanket," laying these +over the plate and sprinkling them with the borax solution when the +plate gets too hot. After a time the deposit of mercury and gold on +the plate will assume a white, efflorescent appearance, and may then be +readily parted from the copper. + +_Another Method_ + +Heat the plate over an open fire, to drive off the mercury; after which, +let it cool, and saturate with dilute sulphuric acid for three hours, +or longer; then sprinkle over the surface a mixture of equal parts of +common salt and sal ammoniac, and heat to redness; then cool, and the +gold scale comes off freely; the scale is then boiled in nitric or +sulphuric acid, to remove the copper, previous to melting. Plates may be +scaled about once in six months, and will under ordinary circumstances +produce about one ounce of clean gold for each superficial foot of +copper surface employed. I always paint the back of the plate with +a mixture of boiled oil and turpentine, or beeswax dissolved in +turpentine, to prevent the acid attacking the copper. + +HOW TO SUPPLY MERCURY TO MORTAR BOXES + +I am indebted for the following to Mr. J. M. Drake, who, speaking of his +experience on the Wentworth Mine, N.S.W., says: + +"Fully 90 per cent of the gold is saved on the outside plates, only a +small quantity remaining in the mortar. The plates have a slope of 2 +in. to 1 ft. No wells are used, the amalgam traps saving any quicksilver +which may leach off the plates. The quicksilver is added every hour +in the mortar. The quantity is regulated by the mill manager in the +following manner: Three pieces of wood, 8 in. wide by 12 in. long by 2 +in. thick, have 32 holes 1 in. deep bored in each of them. These holes +will just take a small 2 oz. phial. The mill manager puts the required +quantity of quicksilver in each bottle and the batteryman empties one +bottle in each mortar every hour; and puts it back in the hole upside +down. Each block of wood lasts eight hours, the duration of one man's +shift." This of course is for a 20-head mill with four mortars or +"boxes." + +I commend this as an excellent mode of supplying the mercury to the +boxes or mortars. The quantity to be added depends on circumstances. A +careless battery attendant will often put in too much or too little +when working without the automatic feeder. I have known an attendant +on suddenly awaking to the fact half through his shift, that he had +forgotten to put in any mercury, to then empty into the stamper box two +or three pounds weight; with what effect may be easily surmised. + +HOW WATER SHOULD ENTER STAMPER BOXES + +The following extract which relates to Californian Gold Mill practices +is from Bulletin No. 6 of the California State Mining Bureau. I quite +agree with the practice. + +"The battery water should enter both sides of the mortar in an even +quantity, and should be sufficient to keep a fairly thick pulp which +will discharge freely through the grating or screen. About 120 cubic +feet of water per ton of crushed ore may be considered an average, or 8 +to 10 cubic feet per stamp per hour. + +"Screens of different materials and with different orifices are used; +the materials comprise wire cloth of brass or steel, tough Russian sheet +iron, English tinned plate, and, quite recently, aluminium bronze. The +'aluminium bronze' plates are much longer lived than either of the other +kinds, and have the further advantage that, when worn out, they can be +sold for the value of the metal for remelting; these plates are bought +and sold by the pound, and are said to contain 95 per cent of copper and +5 per cent of aluminium. Steel screens are not so much used, on account +of their liability to rust." + +I have had no experience with the aluminium bronze screen. I presume, +however, that it is used only for mills where mercury is not put in the +mortars, otherwise, it would surely become amalgamated. The same remark +applies to brass wire cloth and tinned plate. Unless the metal of which +they are composed will not readily amalgamate with mercury, I should be +chary of using new screen devices. Mercury is a most insidious metal +and is often found most unexpectedly in places in the battery where +it should not be. Probably aluminium steel would be better than any +substance mentioned. It would be hard, light, strong, and not readily +corrodible. I am not aware if it has been tried. + +Under the heading of "Power for Mills" the following is taken from the +same source. + +POWER FOR MILLS + +"As the Pelton wheel seems to find the most frequent application in +California, it may be convenient for millmen to have the following rule, +applicable to these wheels: + +"When the head of water is known in feet, multiply it by 0.0024147, +and the product is the horse-power obtainable from one miner's inch of +water. + +"The power necessary for different mill parts is: + + For each 850lb. stamp, dropping 6 in. 95 times per minute, + 1.33 h.-p. + For each 750lb. stamp, dropping 6 in. 95 times per minute, + 1.18 h.-p. + For each 650lb. stamp, dropping 6 in. 95 times per minute, + 1.00 h.-p. + For an 8-inch by 10-inch Blake pattern rock-breaker + 9.00 h.-p. + For a Frue or Triumph vanner, with 220 revolutions per min. + 0.50 h.-p. + For a 4-feet clean-up pan, making 30 revolutions per min. + 1.50 h.-p. + For an amalgamating barrel, making 30 revolutions per min. + 2.50 h.-p. + For a mechanical batea, making 30 revolutions per min. + 1.00 h.-p." + +The writer has had small practical experience of the working of that +excellent hydraulic motor, the Pelton wheel, but if by horse-power in +the table given is meant nominal horse-power, it appears to be high. +Working with 800 cwt. stamps, 80 blows a minute, one horse-power nominal +will be found sufficient with any good modern engine, which has no +further burden than raising the stamps and pumping the feed water. It is +always well, however, particularly when providing engine power, to err +on the right side, and make provision for more than is absolutely needed +for actual battery requirements. This rule applies with equal potency to +pumping engines. + +TO AVOID LOSS IN CLEANING UP + +The following is a hint to quartz mill managers with respect to that +common source of loss of gold involved in the almost inevitable loss +of mercury in cleaning up operations. I have known hundreds of pounds' +worth of gold to be recovered from an old quartz mill site by the simple +process of washing up the ground under the floor. + +If you cannot afford to floor the whole of the battery with smooth +concrete, at all events smoothly concrete the floor of the cleaning-up +room, and let the floor slope towards the centre: where a sink is +provided. Any lost mercury must thus find its way to the centre, where +it will collect and can be panned off from time to time. Of course an +underground drain and mercury trap must be provided. + +IRON EXTRACTOR + +When using self-feeders, fragments of steel tools are especially liable +to get into the battery boxes or other crushing appliance where they +sometimes cause great mischief. I believe the following plan would be a +practicable remedy for this evil. + +By a belt from the cam or counter shaft, cause a powerful electric +magnet to extract all magnetic particles; then, by a simple ratchet +movement, at intervals withdraw the magnet and drop the adhering +fragments into a receptacle by automatically switching off the electric +current. A powerful ordinary horseshoe magnet might probably do just as +well, but would require to be re-magnetised from time to time. + +TO SILVER COPPER PLATES + +To silver copper plates, that is, to amalgamate them on the face with +mercury, is really a most simple operation, though many batterymen make +a great mystery of it. Indeed, when I first went into a quartz mill the +process deemed necessary was not only a very tedious one, but very dirty +also. + +To amalgamate with silver, in fact, to silver-plate your copper without +resort to the electro-plating bath, take any old silver (failing that, +silver coin will do, but is more expensive), and dissolve it in somewhat +dilute nitric acid, using only just sufficient acid as will assist the +process. After some hours place the ball of amalgam in a piece of strong +new calico and squeeze out any surplus mercury. + +About an ounce of silver to the foot of copper is sufficient. To apply +it on new plates use nitric acid applied with a swab to free the surface +of the copper from oxides or impurities, then rub the ball of amalgam +over the surface using some little force. It is always well when coating +copper plates with silver or zinc by means of mercury to let them stand +dry for a day or two before using, as the mercury oxidises and the +coating metal more closely adheres. + +Only the very best copper plate procurable should be used for battery +tables; bad copper will always give trouble, both in the first "curing," +and after treatment. It should not be heavily rolled copper, as the +more porous the metal the more easily will the mercury penetrate and +amalgamate. I cannot agree that any good is attained by scouring the +plates with sand and alkalies, as recommended in some books on the +subject; on the contrary, I prefer the opposite mode of treatment, and +either face the plates with nitrate of silver and nitrate of mercury, +or else with sulphate of zinc and mercury, in the form of what is +called zinc amalgam. If mine water, which often contains a little free +sulphuric acid, is being used, the latter plan is preferable. + +The copper should be placed smoothly on the wooden table and secured +firmly thereto by copper tacks. If the plate should be bent or buckled, +it may be flattened by beating it with a heavy hammer, taking care to +interpose a piece of inch-thick soft wood between hammer and plate. + +To coat with mercury only, procure some nitrate of mercury. This is +easily made by placing mercury in an earthenware bowl, pouring somewhat +dilute nitric acid on it, and letting it stand till the metallic mercury +is changed to a white crystal. Dense reddish-brown fumes will arise, +which are injurious if breathed, so the operation should be conducted +either in the open air, or where there is a draught. + +Having your silvering solution ready, which is to be somewhat diluted +with water, next take two swabs, with handles about 12 inches long, dip +the first into a basin containing dilute nitric acid, and rub it rapidly +over about a foot of the surface of the plate; the oxide of copper will +be absolutely removed, and the surface of the copper rendered pure and +bright; then take the other swab, wet with the dilute nitric of mercury, +and pass it over the clean surface, rubbing it well in. Continue this +till the whole plate has a coating of mercury. It may be well to go +over it more than once. Now turn on the water and wash the plate clean, +sprinkle with metallic mercury, rubbing it upwards until the plate will +hold no more. + +A basin with nitrate of mercury may be kept handy, and the plates +touched up from time to time for a few days until they get amalgamated +with gold, after which, unless you have much base metal to contend with, +they will give no further trouble. + +It must be remembered, however, that an excessive use of nitric acid +will result in waste of mercury, which will be carried off in a milky +stream with the water; and also that it will cause the amalgam to become +very hard, and less active in attracting other particles of gold. + +If you are treating the plate with nitrate of silver prepared as already +mentioned, clean the plate with dilute nitric acid, rub the surface with +the ball of amalgam, following with the swab and fairly rubbing in. It +will be well to prepare the plate some days before requiring to use +it, as a better adhesion of the silver and copper takes place than if +mercury is applied at once. + +To amalgamate with zinc amalgam, clean the copper plate by means of a +swab, with fairly strong sulphuric acid diluted with water; then while +wet apply the zinc-mercury mixture and well rub in. To prepare the +zinc-amalgam, clip some zinc (the lining of packing cases will do) +into small pieces and immerse them in mercury after washing them with +a little weak sulphuric acid and water to remove any coating of oxide. +When the mercury will absorb no more zinc, squeeze through chamois +leather or calico (as for silver amalgam), and well rub in. The plate +thus prepared should stand for a few days, dry, before using. If, before +amalgamation with gold takes place, oxide of copper or other scum should +rise on this plate a little very dilute sulphuric acid will instantly +remove it. + +Sodium and cyanide of potassium are frequently used in dressing-plates, +but the former should be very sparingly employed, as it will often +do more harm than good by taking up all sorts of base metals with the +amalgam, and so presenting a surface which the gold will pass over +without adhering to. Where water is scarce, and is consequently used +over and over again, lime may be added to the pulp, or, if lime is not +procurable, wood ashes may be used. The effect is two-fold; the lime +not only tends to "sweeten" sulphide ores and keep the tables clean, +but also causes the water to cleanse itself more quickly of the slimes, +which will be more rapidly precipitated. When zinc amalgam is used, +alkalies would, of course, be detrimental. + +When no other water than that from the mine is available, difficulties +often arise owing to the impurities it contains. These are various, +but among the most common are the soluble sulphates, and sometimes free +sulphuric acid evolved by the oxidisation of metallic sulphides. In the +presence of this difficulty, do one of two things; either _utilise_ or +_neutralise_. In certain cases, I recommend the former. Sometime since +I was treating, for gold extraction, material from a mine which was very +complex in character, and for which I coined the term "polysynthetic." +This contained about half a dozen different sulphides. The upper parts +of the lode being partially oxidised, free sulphuric acid (H2SO4) was +evolved. I therefore, following out a former discovery, added a little +metallic zinc to the mercury in the boxes and on the plates with +excellent results. When the free acid in the ore began to give out in +the lower levels I added minute quantities of sulphuric acid to the +water from time to time. I have since found, however, that with some +water, particularly West Australian, the reaction is so feeble (probably +owing to the lime and magnesia present) as to make this mode of +treatment unsuitable. + +HOW TO MAKE A DOLLY + +I have seen some rather elaborate dollies, intended to be worked with +amalgamating tables, but the usual prototype of the quartz mill is +set up, more or less, as follows: A tree stump, from 9 in. to a foot +diameter, is levelled off smoothly at about 2 ft. from the ground; on +this is firmly fixed a circular plate of 1/2 in. iron, say 9 in. in +diameter; a band of 3/16 in. iron, about 8 or 9 in. in height, fits +more or less closely round the plate. This is the battery box. A beam +of heavy wood, about 3 in. diameter and 6 ft. long, shod with iron, +is vertically suspended, about 9 in. above the stump, from a flexible +sapling with just sufficient spring in it to raise the pestle to the +required height. About 2 ft. from the bottom the hanging beam is pierced +with an augur hole and a rounded piece of wood, 1 1/2 in. by 18 in., +is driven through to serve as a handle for the man who is to do the +pounding. His mate breaks the stone to about 2 in. gauge and feeds the +box, lifting the ring from time to time to sweep off the triturated +gangue, which he screens through a sieve into a pan and washes off, +either by means of a cradle or simply by panning. In dollying it +generally pays to burn the stone, as so much labour in crushing is thus +saved. A couple of small kilns to hold about a ton each dug out of a +clay bank will be found to save fuel where firewood is scarce, and will +more thoroughly burn the stone and dissipate the base metals, but it +must be remembered that gold from burnt stone is liable to become so +encrusted with the base metal oxides as to be difficult to amalgamate. + +ROUGH WINDLASS + +Make two St. Andrew's crosses with four saplings, the upper angle being +shorter than the lower; fix these upright, one at each end of the shaft; +stay them together by cross pieces till you have constructed something +like a "horse," such as is used for sawing wood, the crutch being a +little over 3 feet high. Select a leg for a windlass barrel, about 6 in. +diameter and a foot longer than the distance between the supports, as +straight as is procurable; cut in it two circular slots about an inch +deep by 2 in. wide to fit into the forks; at one end cut a straight slot +2 in. deep across the face. Now get a crooked bough, as nearly the shape +of a handle as nature has produced it, and trim it into right angular +shape, fit one end into the barrel, and you have a windlass that will +pull up many a ton of stuff. + +PUDDLER + +This is made by excavating a circular hole about 2 ft. 9 in. deep and, +say 12 ft. in diameter. An outer and inner wall are then constructed of +slabs 2 ft. 6 in. in height to ground level, the outer wall being thus +30 ft. and the inner 15 ft. in circumference. The circular space between +is floored with smooth hardwood slabs or boards, and the whole made +secure and water-tight. In the middle of the inner enclosure a +stout post is planted, to stand a few inches above the wall, and the +surrounding space is filled up with clay rammed tight. A strong iron pin +is inserted in the centre of the post, on which is fitted a revolving +beam, which hangs across the whole circumference of the machine +and protrudes a couple of feet or so on each side. To this beam are +attached, with short chains, a couple of drags made like V-shaped +harrows by driving a piece of red iron through a heavy frame, shaped as +a rectangular triangle. + +To one end of the beam an old horse is attached, who, as he slowly walks +round the circular track, causes the harrows and drags to so puddle +the washdirt and water in the great wooden enclosure that the clay is +gradually disintegrated, and flows off with the water which is from time +to time admitted. The clean gravel is then run through a "cradle," "long +Tom," or "sluice," and the gold saved. This, of course, is the simplest +form of gold mining. In the great alluvial mines other and more +intricate appliances are used but the principle of extraction is the +same. + +A MAKESHIFT PUMP + +To make a temporary small "draw-lift" pump, which will work down to +a hundred feet or more if required, take a large size common suction +Douglas pump, and, after removing the top and handle, fix the pump as +close to the highest level of the water in the shaft as can be arranged. +Now make a square water-tight wooden column of slightly greater capacity +than the suction pipe, fix this to the top of the pump, and by means +of wooden rods, work the whole from the surface, using either a longer +levered handle or, with a little ingenuity, horse-power. If you can +get it the iron downpipe used to carry the water from the guttering of +houses is more easily adapted for the pipe column; then, also, iron pump +rods can be used but I have raised water between 60 and 70 feet with a +large size Douglas pump provided only with a wooden column and rods. + +SQUEEZING AMALGAM + +For squeezing amalgam, strong calico, not too coarse, previously soaked +in clean water, is quite as good as ordinary chamois leather. Some gold +is fine enough to escape through either. + +MERCURY EXTRACTOR + +The mercury extractor or amalgam separator is a machine which is very +simple in construction, and is stated to be most efficient in extracting +quicksilver from amalgam, as it requires but from two to three minutes +to extract the bulk of the mercury from one hundred pounds of amalgam, +leaving the amalgam drier than when strained in the ordinary way by +squeezing through chamois leather or calico. The principle is that +of the De Laval cream separator--i.e., rapid centrifugal motion. +The appliance is easily put together, and as easily taken apart. The +cylinder is made of steel, and is run at a very high rate of speed. + +The general construction of the appliance is as follows: The casing or +receiver is a steel cylinder, which has a pivot at the bottom to receive +the step for an upright hollow shaft, to which a second cylinder of +smaller diameter is attached. The second cylinder is perforated, and +a fine wire cloth is inserted. The mercury, after passing through the +cloth, is discharged through the perforations. When the machine +is revolved at great speed, the mercury is forced into the outside +cylinder, leaving the amalgam, which has been first placed in a calico +or canvas bag, in a much drier state than it could be strained by hand. +While not prepared to endorse absolutely all that is claimed for this +appliance, I consider that it has mechanical probability on its side, +and that where large quantities of amalgam have to be treated it will be +found useful and effective. + +SLUICE PLATES + +I am indebted to Mr. F. W. Drake for the following account of sluice +plates, which I have never tried, but think the device worth attention: + +"An addition has been made to the gold-saving appliances by the placing +of what are called in America, 'sluice plates' below the ordinary table. +The pulp now flows over an amalgamating surface, 14 ft. long by 4 ft. +wide, sloping 1 1/2 in. to the foot, and is then contracted into a +copper-plated sluice 15 ft. long by 14 in. wide, having a fall of 1 in. +to the foot. Our mill manager (Mr. G. C. Knapp) advocated these sluice +plates for a long time before I would consent to a trial. I contended +that as we got little or no amalgam from the lower end of our table +plates there was no gold going away capable of being recovered by copper +plates; and even if it were, narrow sluice plates were a step in the +wrong direction. If anything the amalgamating surface should be widened +to give the particles of gold a better chance to settle. His argument +was that the conditions should be changed; by narrowing the stream and +giving it less fall, gold, which was incapable of amalgamation on the +wide plates, would be saved. We finally put one in, and it proved +so successful that we now have one at the end of each table. The +per-centage recovered on the sluice plates, of the total yield, varies, +and has been as follows:--October, 9.1 per cent; November, 6.9 per cent; +December, 6.4 per cent; January, 4.3 per cent; February, 9.3 per cent." + +MEASURING INACCESSIBLE DISTANCES + +To ascertain the width of a difficult gorge, a deep river, or +treacherous swamp without crossing and measuring, sight a conspicuous +object at the edge of the bank on the farther side; then as nearly +opposite and square as possible plant a stake about five feet high, walk +along the nearer margin to what you guess to be half the distance across +(exactitude in this respect is not material to the result), there plant +another stake, and continuing in a straight line put in a third. The +stakes must be equal distances apart and as nearly as possible at a +right angle to the first line. Now, carrying in hand a fourth stake, +strike a line inland at right angles to the base and as soon as sighting +over the fourth stake, you can get the fourth and second stakes and +the object on the opposite shore in line your problem is complete. The +distance between No. 4 and No. 3 stakes is the same as that between No. +1 and the opposite bank. + +TO SET OUT A RIGHT ANGLE WITH A TAPE + +Measure 40 ft. on the line to which you wish to run at right angles, and +put pegs at A and B; then, with the end of the tape held carefully at +A, take 80 ft., and have the 80 ft. mark held at B. Take the 50 ft. mark +and pull from A and B until the tape lies straight and even, you will +then have the point C perpendicular to AB. Continue straight lines by +sighting over two sticks in the well-known way. + +_Another method_.--Stick a pin in each corner of a square board, and +look diagonally across them, first in the direction of the line to which +you wish to run at right angles, and then for the new line sight across +the other two pins. + +A SIMPLE LEVELLING INSTRUMENT + +Fasten a common carpenter's square in a slit to the top of a stake by +means of a screw, and then tie a plumb-line at the angle so that it +may hang along the short arm, when the plumb-line hangs vertically +and sights may be taken over it. A carpenter's spirit-level set on an +adjustable stand will do as well. The other arm will then be a level. + +Another very simple, but effective, device for finding a level line is +by means of a triangle of wood made of half-inch boards from 9 to 12 +ft. long. To make the legs level, set the triangle up on fairly level +ground, suspend a plummet from the top and mark on the cross-piece where +the line touches it. Then reverse the triangle, end for end, exactly, +and mark the new line the plumb-line makes. Now make a new mark exactly +half way between the two, and when the plumb-line coincides with this, +the two legs are standing on level ground. For short water races this is +a very handy method of laying out a level line. + +TO MEASURE THE HEIGHT OF A STANDING TREE + +Take a stake about your own height, and walking from the butt of the +tree to what you judge to be the height of the timber portion you want, +drive your stake into the ground till the top is level with your eyes; +now lie straight out on your back, placing your feet against the stake, +and sight a point on the tree. AB equals BC. If BC is, say 40 ft., that +will be the height of your "stick of timber." Thus, much labour may be +saved in felling trees the timber portion of which may afterwards be +found to be too short for your purpose. + +LEVELLING BY ANEROID BAROMETER + +This should be used more for ascertaining relatively large differences +in altitudes than for purposes where any great nicety is required. +For hills under 2000 ft., the following rule will give a very close +approximation, and is easily remembered, because 55 degrees, the assumed +temperature, agrees with 55 degrees, the significant figures in the +55,000 factor, while the fractional correction contains _two fours_. + +Observe the altitudes and also the temperatures on the Fahrenheit +thermometer at top and bottom respectively, of the hill, and take the +mean between them. Let B represent the mean altitude and b the mean +temperature. Then 55000 X B - b/B + b = height of the hill in feet for +the temperature of 55 degrees. Add 1/440 of this result for every degree +the mean temperature exceeds 55 degrees; or subtract as much for every +degree below 55 degrees. + +TO DETERMINE HEIGHTS OF OBJECTS + +_By Shadows_ + +Set up vertically a stick of known length, and measure the length of its +shadow upon a horizontal or other plane; measure also the length of +the shadow thrown by the object whose height is required. Then it will +be:--As the length of the stick's shadow is to the length of the stick +itself, so is the length of the shadow of the object to the object's +height. + +_By Reflection_ + +Place a vessel of water upon the ground and recede from it until you see +the top of the object reflected from the surface of the water. Then it +will be:--As your horizontal distance from the point of reflection is +to the height of your eye above the reflecting surface, so is the +horizontal distance of the foot of the object from the vessel to its +altitude above the said surface. + +_Instrumentally_ + +Read the vertical angle, and multiply its natural tangent by the +distance between instrument and foot of object; the result is the +height. + +When much accuracy is not required vertical angles can be measured by +means of a quadrant of simple construction. The arc AB is a quadrant, +graduated in degrees from B to A; C, the point from which the plummet P +is suspended, being the centre of the quadrant. + +_When_ the sights AC are directed towards any object, S, the degrees +in the arc, BP, are the measure of the angle of elevation, SAD, of the +object. + +TO FIND THE DEPTH OF A SHAFT + +_Rule_:--Square the number of seconds a stone takes to reach the bottom +and multiply by 16. + +Thus, if a stone takes 5 seconds to fall to the bottom of a shaft-- + +5 squared = 25; and 25 X 16 = 400 feet, the required depth of shaft. + +DESCRIPTION OF PLAN FOR RE-USING WATER + +Where water is scarce it may be necessary to use it repeatedly. In a +case of this kind in Egypt, the Arab miners have adopted an ingenious +method which may be adapted to almost any set of conditions. At a is a +sump or water-pit; b is an inclined plane on which the mineral is washed +and whence the water escapes into a tank c; d is a conduit for taking +the water back to a; e is a conduit or lever pump for raising the +water. A certain amount of filtration could easily be managed during the +passage from c to a. + +COOLING COMPOUND FOR HEATED BEARINGS + +Mercurial ointment mixed with black cylinder oil and applied every +quarter of an hour, or as often as expedient. The following is also +recommended as a good cooling compound for heavy bearings:--Tallow 2 +lb., plumbage 6 oz., sugar of lead 4 oz. Melt the tallow with gentle +heat and add the other ingredients, stirring until cold. + +CLEANING GREASY PLUMMER BLOCKS + +When, through carelessness or unpreventable cause, plummer blocks +and other detachable portions of machinery become clogged with sticky +deposits of grease and impurities, a simple mode of cleansing the same +is to take about 1000 parts by weight of boiling water, to which add +about 10 or 15 parts of ordinary washing soda. Keep the water on the +boil and place therein the portions of the machine that are to be +cleaned; this treatment has the effect of quickly loosening all grease, +oil, and dirt, after which the metal is thoroughly washed and dried. The +action of the lye is to form with the grease a soap soluble in water. To +prevent lubricating oil hardening upon the parts of the machinery when +in use, add a third part of kerosene. + +AN EXCELLENT ANTI-FRICTION COMPOUND + +For use on cams and stamper shanks, which will be harmless should it +drop into the mortar or stamper boxes, is graphite (black-lead) and +soft soap. When the guides are wooden, the soft soap need not be added; +black-lead made into a paste with water will act admirably. + +TO CLEAN BRASS + +Oxalic acid 1 oz., rotten stone 6 oz., powdered gum arabic 1/2 oz., +sweet oil 1 oz. Rub on with a piece of rag. + +A SOLVENT FOR RUST + +It is often very difficult, and sometimes impossible, to remove rust +from articles made of iron. Those which are very thickly coated are +most easily cleaned by being immersed in a nearly saturated solution +of chloride of tin. The length of time they remain in this bath is +determined by the thickness of the coating of rust. Generally from +twelve to twenty-four hours is long enough. + +TO PROTECT IRON AND STEEL FROM RUST + +The following method is but little known, although it deserves +preference over many others. Add 7 oz. of quicklime to 1 3/4 pints +of cold water. Let the mixture stand until the supernatant fluid is +entirely clear. Then pour this off, and mix with it enough olive oil +to form a thick cream, or rather to the consistency of melted and +re-congealed butter. Grease the articles of iron or steel with this +compound, and then wrap them up in paper, or if this cannot be done, +apply the mixture somewhat more thickly. + +TO KEEP MACHINERY FROM RUSTING + +Take 1 oz. of camphor, dissolve it in 1 lb. of melted lard; mix with +it (after removing the scum) as much fine black-lead as will give it an +iron colour; clean the machinery, and smear it with this mixture. After +twenty-four hours rub off and clean with soft, linen cloth. This mixture +will keep machinery clean for months under ordinary circumstances. + +FIRE-LUTE + +An excellent fire-lute is made of eight parts sharp sand, two parts good +clay, and one part horse-dung; mix and temper like mortar. + +ROPE-SPLICING + +A short splice is made by unlaying the ends of two pieces of rope to a +sufficient length, then interlaying them, draw them close and push the +strands of one under the strands of the other several times. This +splice makes a thick lump on the rope and is only used for slings, +block-straps, cables, etc. + + + + + +End of the Project Gutenberg EBook of Getting Gold, by J. C. F. 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