IN our last issue we gave an account of the greatest silver-lead mine in the world, the Broken Hill Proprietary of the Barrier Range, New South Wales. It is now announced that a new silver-lead discovery in the same district perhaps equals in extent this great mine. The following particulars of a mine in Queensland, Australia, the Mount Morgan, the greatest gold mine in the world, will also be of interest. The balance sheet for the half year just ended shows that the receipts for the six months were $3,738,675, including about $75,000 carried forward from the previous half-year's operations. Out of this $2,875,000 have been distributed in dividends and about the same amount has been carried forward as was brought into the account. The dividends declared for the first nine months of the present year amount on an average to $500,000 a month, or $4,500,000. The average production of gold is over 1,000 ounces per day, and it is stated that' the amount oi ore iii sight would warrant even a larger plant than is in use. The ore is refractory and lias given consid-; erable trouble in attaining a satisfactory extraction, but as its average value is over four ounces to the ton, there is a good margin to work on. The orejs treated by chlorination in barrels, usingthe plant, to which process the ore is admirably "suited. One impression that we gather from these accounts as from those of the Broken Hill mine is that the properties are not only ably but honestly administered and in this respect are an example to rnanyjindertakings in other countries. Mount Morgan Mine and Newberry-Vautin Process. EDITOR ENGINEERING AND MINING JOURNAL: SIR: An article appeared in your issue of October 12th. page 811, in which you gave some particulars of the Mount Morgan Mine, Queensland, which, as far as the figures go, I quite indorse, but the concluding part, in which you state that " the ore is treated by el dor i nation in barrel*, us- ing the Newberry-Vautin plant, to which process the ore is admirably suited.'' This statement is incorrect. The Newberry-Vautin plant originally erected has been abandoned for some years. The process now in use is the Mears chlorination process, using chlorine gas under pressure (of chlorine) in a revolving vessel or barrel (an American invention). The alleged improvement of Newberry-Vautin was air or steam pressure applied to the ore mass after the pressure of chlorine had been ob- tained, for which they got a patent. The latter invention was certainly new. Where air pressure ha* been used it has been abandoned. Yours truly, CHI. OH INK. SYDNEY, Australia. November 27th. 1X83. THE ENGINEE 8[C air ai< Aq si' mittal. Here we have two kinds of metallic iron, quick.silve: sulphate, and in the ore sulphides, antimonides, arsenides, 1 dides, metallic silver, and as bases copper, lead, zinc, iron, c? all of the alkalies and alkaline earths so that there are an in sible reactions which can be imagined. If one works out the the Berthelot plan of thermo-chemic reactions, that the the one which develops or absorbs the greatest number of 1 will have the choice of some two hundred series of equatio that was the number reached by one experimenter in inve true inwardness of the matter, the final outcome being as pro before the calculations were begun. Mr. Eissler has made a good point in f rowning upon the ii use of ' ' chemicals " in amalgamation. Every mill man kn< sage-brush extract, tobacco juice, etc., are not efficaceous Mr. Eissler himself advocates the use of free sulphuric acid ; to oxidize chalcopyrite to bluestone. If some of our mill n five or ten stamps, two or four pans, one or two settlers anc to work on amalgamation without chemicals, repeating on th the experiments of Mr. Arnold Hague, they would probably supposed "medicines" could be suppressed without being mi^ a few ounces, or even up to four pounds, of bluestone in < charge seems ridiculous. If the experiment is tried in a glase salt and a little scrap iron on the bottom, it will be foun< copper is at once precipitated in the metallic state on the reduced to subchloride from dichloride, as the most commc theory requires. And after chloridizing, roasting with tht per cent, or more in the furnaces, it seems absurd to add sail pans, as Mr. Eissler did at Mineral Hill. There is almost alw of salt, and such excess is detrimental in two ways: by co mercury as calomel, and by leaching out the silver chloride slimes. Still, with its defects, Mr. Eissler'** book is a good one. good deal of hitherto unpublished records, and bears on e mark of the experienced metallurgist, not a mere maker of b CORKESPONDENCE, We invite correspondence upon matters of interest to the industries metallurgy. Communications should invariably be accompanied witl address of the writer. Initials only will be published when so request All letters should be addressed to the MANAGING EDITOR. We do not hold ourselves responsible for the opinions expressed by < rt Value of the Machinery and Supply Column, EDITOR ENGINEERING AND MINING JOURNAL : SIR: ' I find your innovation of apprising you Machinery Wanted of great value. Yours truly, ElCHARD j. MARQUETTE, Mich., Sept. 20th, 1889. Minim Gypsum, EDITOR ENGINEERING AND MINING JOURNAL : SIR : As a subscriber to your paper, I have been unable to ticle treating of gypsum mining in the United States. I find gypsum in your annual list of mineral products, but J able to find out in which States it is mined. Having lately large bed of this mineral in Arkansas, I would be very thai for information as to which States it is mined in, as I intern if competition does not stand in the way. I of course know Eastern markets only Nova Scotia gypsum is used. [Gypsum is a hydrated sulphate of lime, its chemical com} expressed by the formula, CaSO 4 2H 2 O. It occurs in vark formations, especially in tertiary deposits. In its transpare state it is known as selenite; when it presents a finely fibre appearance it is termed satin spar, and the pure, milky \v varieties are called alabaster. Production. In this country the principal sources of Ohio and Michigan. The production of the latter ( was 54,810 short tons. The average price of land plaster \v and of calcined plaster $10 per ton or $1.50 per barrel of 300 the total product, 28,794 tons were for use as land plaster a? OA\; jo 8qq. QJLTS SHIAYOIJOJ aqj, -QJO oq^. ui ^uaipaaSui ^UE^SQOO AjjrBj B si aaAHg q; ^q; SAYoqs ^oqB^ iJpu'Bjg; raojj wo pB8f-j:aA|is jo raiq lq A^SS-B uy fl8AV 8U J8AJIS JO jqujapisuoo 12 SUTB^UDO puB JO SI '.68813 8q^ A*q U88S o no; J0d 'a:8A{is pu^ foao o uoq. ad zoQ9 'J8A^is '. '^uao aod g.^^ 'p^a^ SUTAVO^OJ aq; SAVoqs ^SS-B aqj, m ao:o p^a{ aq^ a^i^un uo;sauiT| aq; ui '^UT^[ '^q'eq; nB^j^ 'uvfprg ^ apoj -B raojj ajo :o sajdni'Bs araos pamra-Bxa pui3 aq; raojj SUTA\O^OJ aq; .jo;i.ija; aq; ui sip aq -1201 ;'Bq; sfBjaumi SUI^JOAN. SuidojaAap jo asodand aq; jo^ saj'Bqs Xu'B jo q;ua;-auo jo 'pauuoj aq X'BUI ;Bq; Xu-Bdraoo Xa-Bipisqns ^U-B jo saj'Bqs aq; jo q;ua;-auo PUB 'aonpojd aq; uodn ^;^Xoj ';uao jad g jo ;uara^d -B jo aq; uodn ^jo;ijaa; S;T jo apqAV aq; pui5[ XjaAa jo spjauira joj s;qSu aq; Xu'BduioQ oaujog q;jo^j aq; raojj pajmbo-B aA-sq sjo; -oaaip aq; ; r Bq; sa;'B;s Xu'BdmoQ oauJog^ ) aq; jo ;jodaj pnuu'B aqj, STq; Xq paAOiuaj uaaq aA'Bq ppoAv padoq SBAV ;i qoiqAv 'sa^inonjip japun 5joo;s aq; UT ssauisnq os qou'Bjq -B jo aoj ^ansssaoau Xauao^'B jo I'Bas s^uudraoQ aq^ ysi\% HA\ou5[ ^i uaqAv pasn'BO S-BA\. jo pap pooS y *asu op 'pa^aodaa J'BJ os ^nq i dn paqsnj aq |^TAV saa^qs pui? -B aq ^qnopou tji saqo-Baa SAvau aq^ naq^\ pa^Avdn n'B aA-Bq ^|ps pu'B 'an^A nt paAOjdini Ap'Baap aA-Bq saj'Bqs ,/JrBJ,, ois -saadxa aq^ jo A'ji'Bioadsa pu-B { siq^ jo aqc^ uj 'Jiiij aaaA\. ^oadsojd aq^ paB ^SBg; aq^ pn^ -Btpj^sny paspdans qoiqAv. auo^s qoia ^jnjjapnoAv aq-; auiB j qn'B^; snoni'Bj aq^ jo ^o uaaq S'Bq aa^-BAv aq^ autua qnis^j aq^ jo aa^BtrBin r ' - NOTES ON THE TREATMENT OF GOLD ORES. BY FLOKENCE O'DRISCOLL, *i ASSOC. M. INST. C.E. OFFICES OF "ENGINEERING," LONDON; AND JOHN WILEY & SONS, NEW YORK. 1889. CONTENTS. INTRODUCTION .... CHAPTER I. SOME OF THE PROPERTIES OP GOLD CHAPTER II. OCCURRENCES CHAPTER III. REMARKS ON THE PROCEDURE OP LATE YEARS LOSSES FREE MILLING . PARAGRAPHS CHAPTER IV. CHAPTER V. REMEDIES . CHAPTER VI. CHAPTER VII. 3 , 12 21 29 66 167 189 390306 NOTES ON THE TREATMENT OF GOLD ORES. INTRODUCTION. IN the following pages an endeavour is made to place- before the public certain particulars on the subject of Gold Ores and their treatment, in such a form, that a reader who has no knowledge of the subject may be able, after perusal, to have some fairly clear idea of the outlines of the matter written upon. It is desired to avoid technicalities and scientific phraseology, so wherever, for sake of brevity, use is made of any such words or ^erms, in the majority of cases, where first used, an explanation by foot-note is appended. No pretension is herein made of having treated the subject exhaustively ; only the essential details are touched upon ; nor is any attempt made to theorise on the formation of veins, or the deposition of gold in them. It has been a very difficult matter to keep the notes within the limits originally laid down ; in some cases this has been exceeded, but when so, it is hoped B 4 . Properties. microscopically it will be found to consist of minute particles of crystalline gold ; but, if a globule of metallic gold be subject to the same flame, the operator may continue blowing for an indefinite period, and no sublimation or altera- tion in the size of the globule will result. MALLEABILITY. One grain of gold may be beaten into leaf until it covers a superficial area of 56 in., and is of a thickness equalling ^To^th f an i ncn - DUCTILITY. One grain of gold may be drawn into a wire of 500 ft. long ; a grain of gold in a globular form is about equal in size to a No. 9 shot, and measures .073015 in. in diameter SOLUBILITY (see pages 5-11). CRYSTALLOGRAPHY. The cubical system ; the most common forms being octahedrons^ and dodeca- hedrons, t NATURAL ALLOYS. Native gold is almost always found alloyed with a proportion of silver ; this varies so greatly in different localities, that no general statement can be made to indicate the proportion ; but the higher the proportion the more closely do the forms approach those of native silver. Rhodium, palladium, mercury, copper, iron, and bismuth are amongst the other metals with which gold is found naturally alloyed; in some deposits it occurs with tellurium, and bismuth in what appears to be a definite chemical combination. VALUE. The value of pure gold at the London Mint is 4Z. 4s. ll^d. per ounce troy; roughly stated at 4s. 3d. per pennyweight and 2d. per grain. J | Particulars regarding value are added so as to make the information on the subject more complete. / A Natural SulpMde 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 oc- currence, but up to the present time this occur- rence has, I believe, never been established as an actual fact. During my investigations on the ore of the Deep Creek mines, New South Wales, I have found in them what I believe to be gold existing as a natural sulphide. The description of this ore will, no doubt, be of in- terest to your readers. The lode is a large, irregular one of pure arsenical pyrites, existing in a felslte dyke near the sea coast. Surrounding it on all sides are micaceous schists, and in the neighborhood is a large hill of granite about 800 feet high. In the lode and the rock immediately adjoining it are large quantities of pyrophyllite, and in some parts ot the mine are deposits of this pure white translucent mineral, but in the ore itself it is a yellow and pale olive green color, and never absent from the pyrites. is Properties. n HYDROCHLORIC ACIDS (aqua-regia), VND NITRIC ACIDS, NITROUS ACIDS, t YANIDES, f other chemical substances under ns which, though very interesting, oiselves of sufficient practical im- From the very first I was much struck with . . the exceedingly fine state of division in which llSCUSSed in this inquiry, the gold existed in the ore. After roasting . , , . , , and very carefully grinding down in an agate luble Salts DV the elements ! 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 gangne so as to leave the gold intact failed to show particles of any larger S" iS^Sr^^SKof the same in certain reactions. ? WS23S3 I 2 are distributed throughout nature X- b iphide. n thll " ! ' eftbnt t0 tMt '"lowing manner : ^TW&Bft^Vafert commonly in combination with It finely and heating for some hour, with a a l or ide of Sodium Or Common Salt. solution of sodium sulphide (Na 83), on decom- posing the filtrate and treating" it for gold, i s fa one o f the most widely dis- By far the largest sources it is also found very the - is *ot a result at the rate of 12 ounces gold per '"' ton. This was repeated several times with the tture me result. This sample came from the lode t the 140-foot level, while samples from the ock Salt ligher levels, where the ore is more oxidized, although carrying the gold in the same degree tore Or leSS in most Waters, in af fineness, do not give as high a percentage of mrio sulphide. riiinal bodies, and to a lesser extent It would appear that all the gold in the pyrites (and I have never found any apart from It), has originally taken its place there as a sul- phide. The following is an analysis of a general sample of the ore : Silica, 13.940%; alumina, 3.592%; lime, 0.9025%; sulphur, 16.584%; irsemc,33.267%;iron, 27.720%; cobalt, 0.964%; nickel, traces; gold, 5 ozs. 3 dwts. 8 grs. per ton; silver, 16 dwts. per ton; total, 99.969%. T. W. T. Atherton, in Eng. and Mining Jour. om. E. Though not in such large they are very widely distributed ; and manner, especially in marine : of sodium and iodide of sodium, .ons, not otherwise in animal or f Gay-Lussac. 6 Properties. Before any compounds of the foregoing are in a state to act as. solvents for gold, decomposition must take place to set "free" the active element, and in the constituents of the earth's crust the chemicals to produce these reactions are found widely distributed. As an illustration of how nature may work, the following is cited : The manufac- turer in order to produce chlorine mixes sulphuric acid, manganese (manganic oxide), and common salt ; sul- phuric acid combines with the sodium and hydrochloric acid is produced ; manganese supplies oxygen to take the hydrogen from hydrochloric acid, thus finally " free- ing" or liberating the chlorine ; the chemical equations for the reactions are as follows : NaCl + H 2 S0 4 HC1 + Na H S0 4 Common salt + Sulphuric acid = Hydrochloric + Sodium hydrogen acid sulphate* 4 H Cl + Mn O 2 C1 2 + 2 H 2 O + Mn 01, Hydrochloric + Manganic = Chlorine + Water + Manga- acid oxide nous Chloride In nature these reactions may take place as in the workshop of the manufacturer. Sulphuric acid is not only a natural product of volcanoes, but it is formed in very large quantities by the decomposition of pyrites or mundicf deposits. Common salt is to be found in the waters percolating the soil of the earth's crust. It is easy to conceive that sulphuric acid and common salt are continually coming into contact and liberating hydro- chloric acid ; this coming into contact with manganese, or other substance with similar properties, finally sets chlorine free. As already noted, wherever masses of pyrites are * Such salts are sometimes called acid sulphates. f A miner's term, which includes all common mixtures of sulphides and arsenides found in mines. Properties. 7 decomposing, the quantity of sulphuric acid found is very great. A large number of other minerals are present,, which with sulphuric acid at once brings about a chemical change ; thus giving rise to the mineral sulphates found in veins and deposits. After these reactions are satisfied, any surplus of sulphuric acid is left free to act upon the common salt contained in the water percolating the de- posits, and hydrochloric acid is formed, which, in turn, coining into contact with an oxidising agent, evolves free chlorine. Pyrites almost invariably contains gold in relatively minute particles ; the decomposition of pyrites, with sub- sequent liberation of chlorine in close proximity to this gold, causes the immediate formation of a gold chloride (Au C1 3 ) soluble in water. The reactions bringing about the liberation of free bromine and iodine, and the formation of soluble gold salts, take place from similar causes and in the same manner as explained in the case of chlorine. Before closing the subject of solubility, it may aid the general understanding of the case to describe briefly how these solvent agencies affect such other metals as are generally associated with pyrites. Although chemical geology is extremely interesting, it is almost an inter- minable subject, therefore a number of intermediate reac- tions which must take place, but do not interfere with the main issue, are purposely omitted. Dealing witk the only important metals affected by the breaking down or decomposition of pyrites deposits : Any carbonates of lime, magnesia, baryta, &c., are at once converted into sulphates by the action of sulphuric acid ; iron is con- verted into oxide, sulphate, and carbonate ; lead into sul- phate and carbonate ; arsenic enters into combination 8 Properties. with iron, lime, &c. ; copper becomes a sulphate or car- bonate ; sulphide of silver decomposing under the condi- tions enumerated, and in the presence of salt water, forms chloride of silver. All these reactions, in all probability, occur before the liberation of free chlorine, bromine, or iodine takes place. In cases where all the sulphuric acid evolved is con- sumed in bringing about the first-mentioned reactions, there is nothing left to form solvents for gold, there- fore the metal remains as it was and where it was prior to the decomposition of the pyrites, and the miner will find it in the gossan of the deposit. That the foregoing reactions take place in nature the following tends to prove : On certain goldfields where the rocks are covered with little or no surface soil, it may be noticed that long lines of brown iron ore (hydrous oxide of iron) cross the field in the direction of the strike of the lodes, sometimes running along the outcrops, in other cases following fissures or cracks on the true strike of the rocks containing the lodes ; this oxide of iron, in many instances, may be traced to quartz veins, and is a pro- duct of decomposing pyrites. Careful examination of the lodes reveals the following : On and near the surface oxide of iron is found in hard compact masses, sometimes botryoidal or stalactitic ; this as far as it extends is called the cap of the lode. Below the cap, the quartz lode proper is met, and on examina- tion it will be found that the joints and surfaces are stained and coated with compact oxide of iron, which also fills some of the cavities in the stone. Deeepr down the lode, the vascular rock, highly charged with oxide of iron and known as gossan, is found in the joints and cavities, in a spongy and friable form ; it is the mineral Properties. 9 matter left after the decomposition of the pyrites, and the removal in solution of soluble substances. Below this, at the water level of the lode, the brown iron ore is entirely lost in the soluble iron salts and decomposing pyrites. And immediately beneath, again, the solid .and unaltered pyrites is found ; in highly mineralised lodes this zone of decomposition is very clearly marked by a line of black friable decomposing mundic with iron in the form of soluble sulphates immediately overlying the still unaltered mineral matter. The gold in this mineral matter in the decomposing zone and in the gossan is found in irregular and, more or less, crystal- line particles ; the sizes of the particles found under similar circumstances vary greatly in different lodes. Sometimes the gossan is very rich in gold, sometimes it appears as if some of the gold had been dissolved out, sometimes it is blank, which naturally leads to the supposition that whatever gold it contained had, at some previous time, been carried off in solution by water; nearer the surface there is strongly confirmative evidence for this supposition. As the lode is traced upwards, the gossan is found if gold-bearing to bear gold and be of the nature described, until the cap is met. The more or less hard compact oxide of iron forming the cap of the lode is found to be impregnated with gold, in entirely different forms to that below. The joints of the stone are frequently found covered with a gold film, so that any one not versed in the subject might often mistake it for a purple iridescence left by an iron-impregnated water ; again, the shape and size of the deposited films are such as to preclude all possibility of their having found their way, through the natural filter-bed of the lode, from the gold-bearing pyrites below, unless carried in solution by 10 Properties. water and there precipitated. The impregnation of the hard compact masses of the cap by microscopically fine gold, is accounted for by the water carrying a solution of both iron and gold, and on evaporation under atmo- spheric action, the gold-impregnated solidified iron oxide is found. A peculiarity of such formation is, that the caps of these lodes are much wider, more confused and indefinite than the lodes beneath ; this is accounted for by the corrosive action of the mineral waters destroying the original confining walls of the lodes and eating back into the country rock. In the distribution of gold through this cap there is another peculiarity observable. Although the lode underneath may be (say) 2 ft. or 3 ft. wide, the cap may be 20 ft., 40 ft., 100 ft. wide or more ; and yet not, so to speak, proportionately dilute in gold, as compared with the narrow body of lode from which it derived its origin. It is generally as rich as the lode beneath, in many cases far richer in patches, yet there are in this great mass many blank patches also. The formation of gold-bearing patches of greater or less rich- ness is accounted for by the belief that from great lengths of the lode, the drainage waters, bearing gold in solution, find their way to the surface in comparatively constricted outlets and precipitate the metal from its solutions, throughout the masses of rock in these outlets which had already been corroded and altered by solvent agencies before mentioned. Although in nature the solvent solutions for gold may be indefinitely dilute, the geological ages are indefinitely long, during which the result of accumulating action brings about tangible results, and though chlorine is of this class, the most widely-spread element, bromine, and Properties, 1 1 iodine, in lesser quantities are continually acting in a similar manner. Nitro-hydrochloric acid (aqua-regia) is the ordinary solvent for gold in most manufactures, but, owing to cost, it is not as yet of value to the gold producer as a collecting medium, Other solutions not compounds of the active elements dealt with, are all distributed throughout nature and are continually carrying on their solvent actions, but in a degree of such lesser magnitude as to be outside the limits of the present inquiry ; should any reader be desirous of investigating the matter further much information will be found in the writings of BischofF, Sterry Hunt, and others. It may be well to reiterate that the description of these reactions is in no way an attempt to theorise upon the origin of auriferous deposits. 12 Occurrences. CHAPTEE II. OCCURRENCES. GOLD exists in nature under widely different condi- tions, which, for the present purpose, may be classed under two heads : ALLUVIAL DEPOSITS. DEPOSITS IN THE MATRIX. ALLUVIAL DEPOSITS. The greatest gold accumulations known are those which have been discovered in the gravels or earthy deposits of long disused river beds and streams, and in places which, from their extent and other indications, appear to have been the beds of seas or lakes. The sizes and forms in which the metal is found are very variable. It is found as " dust, " " nuggets, " thin plates, flakes, crystals, &c. Miners apply the word " nugget " in a very general sense ; any piece of gold weighing above two or three pennyweights being termed a " nugget," while the same name is given to all large masses found. The individual weight of many have exceeded 1500 oz. troy, and in some instances over 2000 oz. in weight has been reached by single pieces. " Dust" covers the infinite variety of sizes from particles so finely divided as to be held in suspension by water for considerable periods of time, up to the size known as " nuggets." There is, however, a variation in name sometimes used, such as " shotty gold " for granular Occurrences. 13 pieces like the smaller sizes of shot. Often a rudimentary form of crystal may be traced in some derivative from the cube ; but though pieces are generally water-worn, many perfect crystals have been found. It may be assumed that crystalline forms are much more common amongst the finer sizes, than in large pieces; micro- scopic examination frequently reveals this to be the case. The precise depths from the surface at which the metal is found, varies, by reason of denudation and other causes, in an almost indefinite manner. In a general sense the richer deposits are obtained in the last few inches of material covering the bedrock, but some of the most remarkable finds yet made have been on or within a few inches from the surface. In the beds of rivers and gorges gold deposits have been found in successive layers or bottoms, one above the other, and when so occurring, though generally divided by alluvium, cases have been known where conglomerate rocks, and even beds of basalt or other igneous rocks, have intervened between the deposits of gold ; such occurrences have given rise to great argument amongst miners as to the difference between true and false bottoms. When deep sinkings are made to reach alluvial deposits, they are known as " deep leads." Sometimes when these are put down or tunnels driven, it is found that the physical features of the country have been entirely altered, and that the ancient river bed, having in it a stratum of gold, has been covered by accumulations so as to become a hill or watershed, consequently the modern river finds quite another channel, frequently far removed. The positions in which large nuggets are found vary in the most extraordinary manner. Some have been 14 Occurrences. picked up amongst the grass roots, others in the roots of uprooted trees, many have been found surrounded by soft soil far above the bedrock ; in fact, frequently, the first indication a miner has of one is either striking: it with o his pick or seeing it shining amongst the mass of sur- rounding earth or debris. The story may be cited of the finding of the "Welcome Stranger," the largest nugget yet discovered. Near Dunnolly, Victoria, two miners, weary and broken down by toil and disappointment, were aimlessly wandering about, having failed to obtain further supplies from the storekeeper who had hitherto given them credit. They felt that they had come to the end of their tether, and " a smoke " was the only solace left for their woes. One of the men preparatory to lighting his pipe, stuck his pick into the ground. It struck something hard and dull sounding, which caused them to investi- gate, the result being in a few minutes the laying bare of a mass of gold weighing 2195 oz. troy, bearing the mark of the pick. Gold is also found as " dust " in the sea sands on the coast of California, New Zealand, and other places, and in the detritus of many rivers. Some of these deposits have been of great value, but many present little or no permanence ; for that which one day is visible and workable may the next be covered deep with sand or carried by currents to other localities. Alluvial gold has generally a smaller proportion of silver and other metals alloyed with it than gold obtained in rocks and veins. The minds of chemical geologists are still exercised in endeavouring to account for this peculiarity. DEPOSITS IN THE MATRIX. The occurrence of gold in rocks and veins presents even greater peculiarities and Occurrences. 1 5 varieties of form than those of the alluvial deposits just dealt with. The following are some of the forms in which it is found: Crystals, specks, flakes, spangles, filaments, branches, wires, threads, leaf-like and sponge- like forms, irregularly shaped lumps of all sizes, from dust-like particles to that which in alluvial gold would be considered large nugget sizes ; and there is known to exist even a finer division than that which may be termed dust ; for in certain cases, where microscopic examination showed no gold, considerable quantities have been obtained by chemical treatment. It is now beyond doubt or argument that by far the greater wealth of gold ore deposits at present known are those wherein the metal exists in finely divided particles disseminated throughout vein structures and deposits. In like manner a very general occurrence of gold is in association with the sulphides and arsenides of iron, and the sulphides of copper, lead, zinc, antimony, and bismuth. The miner as a rule classes any mixture of the above under the general term mundic or pyrites. Although by some it is considered a debatable question as to whether gold is chemically combined or mecha- nically held in these compounds, the balance of evidence is strongly in favour of the latter condition, and to this view most of the leading metallurgists of the day are inclined. When so occurring it is indisputable that in the majority of cases gold is in a state of extreme division, so much so, that to describe it as fiour would be a poor illustration of its finely divided condition. There are certain large auriferous districts where the metal is found almost entirely associated with the above-mentioned compounds, but these districts are not the sole localities wherein it is so deposited ; in gold-producing districts 16 Occurrences. where the veins carry free gold, patches of gold-bearing sulphides are frequently met with ; and in many localities free gold and gold-bearing sulphides are very evenly mixed throughout the deposits. The popular and eagerly sought auriferous deposits are those in which gold is here and there visible in irregularly shaped particles, though such an occurrence by no means denotes richer deposits than those carrying invisible gold or gold-bearing compounds ; indeed, it is frequently found that the latter are more dependable in their return of metal. There are numberless instances of the occurrence in veins of heavy gold-bearing patches of stone of great value, where the metal was in large and irregularly shaped particles, sometimes in flakes and plates, like ham in a pile of sandwiches. One of the most valuable of these discoveries was in the Hill End Mine, near Sydney, New South Wales. The patch of stone in question was about 5 ft. high, and on an average 1 ft. wide and 6 in. thick, it was full of gold in the form of threads, wires, lumps, and irregularly shaped particles, and its value was, in round figures, 15,000/. Another form in which gold occurs is that in the world-famous Mount Morgan Mine, near Rockhampton, Queensland. The deposit presents several interesting features, as may be seen from the following brief description, which embodies the observations of Mr. Jack, the Queensland Government geologist. The mountain, situated about thirty miles from the sea, is surrounded by a tableland, above which it rises about 400 ft. ; the summit being 1225 ft., and the average altitude of the table-land about 800 ft. above sea level. The country rock consists of a sandstone forma- tion, with occasional masses of hard shale, and in the Occurrences. 17 immediate locality of the mountain it is intersected in every direction with intrusive masses of igneous rocks, such as rhyolite and dolerite. At the time of Mr. Jack's report the geological evidence seemed to prove to him that the mountain has resulted from the upward flow of a thermal spring carrying silicious, -argillaceous, and other matter, in a semi-liquid, mud-like mass. The summit of the mountain, when opened out, was found to be a mass of silicious brown hematite ironstone with a stalactite structure, together with what appeared to be a cellular silicious sinter ; this had a frothy appearance, and was sometimes light like pumice- stone. In one part of the first cutting on the summit was found a band of kaolin in various states of purity. Throughout the whole mass gold, exceptionally free from alloy, occurred in the most minute powder, rarely visible to the unaided eye, to the amount of from 5 oz. to 8 oz. to the ton of deposit; it assays 99.7 fine; the alloy is copper with minute traces of iron, and it is worth 4/. 4s. 8d. per ounce troy. Quarries lower down the mountain revealed even more complexity in the deposited mass : Brown hematite, red hematite, aluminous iron ochre, white silicious deposits, soft aluminite, masses of magnesian and aluminous silicates, and loose silicious sinter, in almost all of which gold occurs similarly and to much the same amount as previously mentioned. The hillsides formed by the overflow are of like character, and carry gold in the same manner as the interior of the hill ; but no gold has yet been obtained in the locality which cannot be traced to the influence of the deposit and the surface indications, resulting from its gradual denudation. When Mr. Jack examined this mountain for the purpose of reporting on it to the Queensland Government, very little work had 18 Occurrences. been done there. The opinions he then expressed are probably those that any other skilled geologist would form with the same data to judge from. As this great deposit is now well opened out, and much is to be seen which could not have been guessed at when Mr. Jack was there, a different explanation is now feasible to that of the " thermal " theory then propounded. Recent investigations would justify the classing of the occurrence as a remarkable and unusual development of the set of causes set forth on pp. 8-10 as an explanation of the deposits found above decomposing pyritous lodes. It seems that this Mount Morgan is the result of aqueous action, by which the deposited portions of a large mundic lode beneath have been carried upwards and accumulated on the surface. That which appears to be silicious sinter of geyser origin is the silicious skeleton from which granular iron pyrites have been dissolved out by natural causes. Specimens exist where one part of a stone is apparently solid pyrites and the other half sinter. In several instances pieces of the solid parts have been treated with nitric acid and the pyrites dis- solved out, then a framework of iron-stained silica was left, not to be distinguished from the silicious sinter of thermal origin. Investigations have revealed the exist- ence of a large pyrites lode underlying the deposit, but this is not yet worked for gold. Within the last five years gold to the value of several millions sterling has been extracted from the ore taken out of the workings, and as far as can be judged from these investigations, the mountain throughout is a mass of heavily charged gold-bearing deposit ; its value is still undeterminable because of the difficulty experienced in obtaining a data as to depth and extent. The gold carried in rocks and veins is sometimes in Occurrences. 1& a crystalline form, but in the majority of instances this is not very clearly defined, though with the smaller particles the edges of the crystals are more apparent ;. often that which appears to the unaided eye to be a thread or film of gold is, upon microscopic examination,, discovered to be an aggregation of more or less dislocated minute crystals one built upon the other. In fact the more closely the occurrence of gold is examined the stronger is the evidence of its deposition from solution in separate and minute particles. Another form in which gold occurs, far more wide- spread, and of incalculably greater aggregate value, than any other yet known, is : the gold carried in the waters of the ocean this is not just now available for general circulation. > That gold is present in all sea water, and may be determined easily, is not a matter of dispute ; it is held in solution, presumably in the form of bromides and iodides ; Sonstadt estimated that it is present to the extent of nearly one grain to the ton of water, or, roughly, to the value of two pence. The early alchemists seem to have stumbled across some traces of this fact in their search after the secret of transmutation. As might be expected, their notions on the subject were extremely visionary and indistinct, and were first given to the world in 1350 by the monk Odomar, who stated that the salt of the sea was the mercury of the philosophers or chief ingredient to be made use of in the composition of the wonderful stone which was to turn all that it touched into gold.^ He found many fol- lowers, among them the famous Bernard of Trdves, who, thinking (as he said) that "the ocean was the mother of gold," set up in 1432 a laboratory on the shores of the * Lazarus Zetznerus, Theatrum Chernicum Argentorati, 1659, de Practica Magistri Odomari, vol. iii., p. 169. 20 Occurrences. Baltic, and there spent nearly eighteen months, experi- menting upon sea- water, without any result.^ Gabriel de Chataigne, the Grand Almoner of Louis XIII., seems to have been more fortunate, for he states that he himself saw transmutation effected by a stone prepared with sea salt,f and some report of this statement no doubt inspired Becher, in the proposal which he made in 1669 to the States General of Holland, to turn the dunes into gold, his offer, according to him, after the favourable report of a committee of chemists, being only rejected on account of the low state of the Dutch exchequer.^ Those curious in such survivals will find a series of ex- periments, intended to show the possibility of the transmu- tation of metals, set out at length in the report of a M. C. Theodore Tiffereau to the French Academy in 1854.1 If M. Tiffereau really did succeed in producing traces of gold by any such process as he describes, his success would seem to be due to the fact that he employed sea-salt as one of his ingredients. " The theory of the formation of veins, and the occurrence of gold therein, also in unstratified rocks, &c., although deeply interesting, is outside the purpose of this inquiry, as is also any record of observations concerning shoots of gold in veins, saddle-back veins, &c., for the reason that to touch upon these ques- tions would only result in incompleteness, and to enter thoroughly into an investigation would lead into so many by-paths, as to extend these notes far beyond their intended limit. * Ibid., Bernard! Trevisani de Alchemia Liber, vol. i., p. 686. t L'Alchimie et les Alchiinistes par Louis Figuier, Paris, 1856. Physica subterranea Becherii Remarks. 21 CHAPTER III. REMARKS ON THE PROCEDURE OF LATE YEARS. WITHOUT in any way attempting to investigate the history of gold, it may be mentioned that from the earliest times of which there is any record apart from the practice of smelting two main principles were followed out in endeavouring to collect gold, no matter in what form it was discovered. These were : 1st. Recognising the relative gravity of the metal, crushed ore was subjected to the action of a stream of water, in order that the force of its gravity might work the golden salvation sought, by bearing the metal to the bottom of the stream, and keeping it there until all else had been carried off. 2nd. The affinity between gold and mercury was recognised and it was believed that the latter possessed the property of absorbing all gold particles, and also of rapidly re-forming into a mass, even after being broken up into minute globules by shaking or friction ; for this reason mercury was put into a mill with gold ore, and either crushed with the ore or agitated through it. In ancient Egypt, many centuries before the Christian era, gold ores were crushed between stones, and the powdered rock and metal afterwards washed by a stream of water over an inclined plane, when all rock particles 22 Remarks. were thus swept away, any gold remaining was secured. T"ery old records also point to the addition of mercury as an agent to facilitate the collection of gold particles ; for this purpose it was either placed below the stream of water, or agitated throughout the mass of ore. As it is with the collection, not the discovery of gold, that these notes will chiefly deal, it will suffice to draw attention to modern practice and developments since the discoveries of gold in California in 1848 and Australia in 1851. One of the most remarkable features noticeable when dealing with this subject is, that although decades of centuries have passed since history tells of the methods employed in saving gold, the self-same principles are still perpetuated, as those which we may imagine to have been adopted by pre-historic man. To-day, in the great majority of countries and places where gold is mined, the two main principles mentioned comprise almost all the cunning brought to bear upon this important problem ; certainly, modifications in procedure have been introduced, but these chiefly tend to developments in crushing rocks, and the fact remains, that every piece of gold saved must possess the inherent quality of withstanding a rush of water, sinking through it and amalgamating with mercury, otherwise it will be washed away and practi- cally lost. A glance at the practice of miners' of forty years ago may be of interest. As soon as a man abandoned prosaic modes of obtaining a livelihood and took to the life of a gold seeker, he then seemed to become imbued with strange characteristics ; a self-conscious air of heroism seemed to surround him. As this increased, so vanished all sense of prudence necessary to successfully regulate everyday life ; thrift, forethought, and reason, gave place Remarks. 23 to a wild infatuation for getting gold, without one thought of ever keeping it. The history of how the trader enriched himself by taking advantage of the swaggering independence and prodigality of the miner, reads, wherever written, as though it were the work of a clever romancer, instead of a plain statement of facts. This strange mannerism seemingly not born of race or country, is the marked characteristic which has shown itself, and will no doubt show itself again, whenever and wherever new gold discoveries are made. It follows as a natural consequence that without being so born, a race of men are bred who will neither be taught nor learn to attend to and conserve their own interests. Amongst miners there has been no greater object of general derision than a man preaching against their accepted methods ; to-day it is almost the same. The miner is hard to convert; he is a conservative of the conservatives in the devotion with which he guards his rule of thumb fallacies, but unfortunately his con- servatism does not apply to the saving of gold ; in this respect he may be considered a liberal of the most pro- nounced type. When the miners of thirty years ago found gold in earth and gravel, they continued the practice adopted by miners in dimly remembered ages ; that which was too small to pick out they attempted to save by setting a- stream of water to wash away the earth and stones with which it was mixed ; it fulfilled its mission by carrying off all particles which had not sufficient weight to withstand the flow of water. When water was scarce the "dirt" was put in cloths or blankets, then shaken high in the air, in the belief that the wind would blow away everything light. * These * As an illustration of this : In the waterless gold-producing dis- 24 Remarks. slap-dash methods having soon exhausted, at any rate so far as to satisfy the miner, the then discovered finds, therefore, the adventurers sought other deposits- and turned their attention to the gold contained in lodes and rocks. They crushed these rocks and applied to the crushings the self-same principles as before, with very much the same result. The sense of sight was of all others the one most trusted; that which could be seen by the unaided eye was sought after and recovery attempted; that which was not seen, though demonstrated by a magnifying glass or assay, was thought of little account, and treated accord- ingly. Various theories were invented by which losses might be accounted for; certain ores were found which would not give the gold visible in them, and some bright genius hit upon the terms "refractory," "rebellious," and " rusty," and, in cases where very fine gold occurred, the term "float gold." The amount of consolation afforded for years past to the miner by the invention of these terms has indeed been infinite, they are used over and over again with most satisfying effect when the mill returns fail to give anything like an approach to assay values. In fact, in many cases whole districts showing by assay to be very rich in gold, have been entirely, or almost entirely, abandoned because of the difficulty experienced in securing the gold. This has resulted from the per- sistent endeavours to continue in the long-trodden paths, tricts of New South Wales, on any windy day, rows of miners may be seen throwing high in the air the "dirt " out of their tin dishes, and so separating a large percentage of the metal from its surroundings. To those not versed in the question, this may seem a very ridiculous proceeding, but in reality, though perhaps slower, it is not such a wasteful method as hydraulic separating; the question of collection by winnowing will be dealt with in another chapter. Remarks. 25 and apply to every class of ores the principles of con- centration in a stream of water, and amalgamation under similar conditions with mercury. In ordinary avocations of life a tradesman would be considered as a species of lunatic if he attempted to carry out watchmakers' work with blacksmiths' tools, yet the miner has as widely dif- ferent propositions put before him as those existing between the trades mentioned, and still he persists in working with only the one old-fashioned and scanty kit of tools. Since set moving by this later influx of gold to the world's circulation, places and things have gone ahead very rapidly, and the same standard by which we judge the miner of forty years ago, should not be applied to-day; what was thoughtless and foolish then is now very much like culpable ignorance. The old-time miner had little or no option, appliances were difficult to obtain, costly when obtained, and the process of getting almost invariably resulted in much chafing delay. Such is not the case at present; there are few parts of the world to which appliances cannot now be sent in the same number of weeks that formerly occupied months in transit ; freights and prices of machinery are much less. The sub- ject has also been studied and written upon, and knowledge is to be had for the picking up ; all through these years, men of common sense, and men of the highest scientific attainments, have spoken and written of the wrongfulness and wastefulness of the methods in vogue ; every opinion herein expressed is but an echo of what has been written and spoken over and over again. But the policy of mining men has ever been, " Take what we can get easily, and don't bother about that which is difficult," together with the often-expressed sentiment, " Oh, we are getting enough." The average miner of to-day will speak as 26 Remarks. though his voice were the voice of a phonograph that had been laid by for forty years had such a contrivance been then invented. Of late years, more deadly by far than the miner as an opponent to the advancement of the science of metallurgy, is the " mining expert," who thrives in the quarters of large cities where share and stock dealing is carried on. Of course there are notable and honourable exceptions, but the trouble is that any one and every one is free to dub himself a Mining Engineer, consequently the true and the false, as far as name is concerned, trade under the same sign. Very frequently the limited information possessed by many of these scientific gentlemen is supplemented by a facility for compiling estimates from picked samples and fanciful assays, rendering them invaluable allies to a certain class of company promoters and their pestilent horde. It is no light and easy task for business men and directors of mining ventures to discriminate without pre- vious knowledge between the sound men and the "frauds" o who make up this body, for to the non-technical mind a semblance of great knowledge is frequently conveyed by a few scientific terms aptly introduced in conversation. There is yet another class that tend to retard advance- ment; these are a large percentage of the fledglings who, without any practical knowledge, are turned out of mining schools and similar institutions. They arrive on the goldfields brimful of enthusiasm and a mass of unassimilated information, without sufficient discrimina- tion or capability to put it to practical use. They con- front the miner with what are, in effect, useless and new- fangled theories, therefore their efforts to instruct him invariably ends in dismal failure, and weds him more firmly to the methods of the ancients. Remarks. 27 It should be remembered by those who deal with the subject, that it is the obsolete traditions and the manner in which they are clung to that are alone deserving of censure. The amount of energy displayed and the degree of perfection reached by the miner is, in many instances, deserving of unmeasured praise. Doubtless in a great measure he has been forced into this by the progressiveness and ability of, and competition between, machinery manufactures. In alluvial and hydraulic mining especially the improvement is marked; by toil and care the gold miner is now enabled to work remunera- tively by taking out what approach millionth parts of the mass with which he deals ; results unparalleled by the records of any other metal worker. A worker in tin, iron, copper, lead, and other ores thinks it well when only tenths and hundreds are run to waste, whereas the gold miner must, practically, in every instance, remove nine hundred and ninety-nine and a frac- tional part per thousand of the whole body of ore before he obtains what he seeks. For instance, with stuff mined and raised from as deep as 200 ft. and 300 ft. below the surface, he can by the collection of from two or three pennyweights of gold, pay a dividend; these two or three pennyweights 48 to 72 grains are the aggregated weight of minute particles of metal disseminated throughout 15,680,000 grains in weight of one ton of dirt. Where the principle of hydraulic mining can be adopted, he has made as low a return as one and a half grains (3 cents^) collected from 15,680,000 grains, a paying concern ; these are results brought about by the working of companies adopting the most advanced methods. * Egleston's "Gold and Silver." 28 Remarks. But with mining, as in everything else, the rapid diffusion of knowledge is dimming the halo of romance which generally surrounds distant and unknown avoca- tions. The typical miner is gradually and surely be- coming extinct, his trade is now dolefully prosaic ; by shrewd investors it is beginning to be regarded as a legiti- mate sphere wherein to embark capital ; thus combination and capital have made the worker a " wages man." The greater number of the most valuable mining pro- perties known, are in the hands of companies, many of which are managed by business men who are prepared to apply to this business the same economical principles as those by which all other successful undertakings are guided. Such men are ready and doubtless anxious to listen to reason, provided the reason be sound and stated with sufficient distinctness. Losses. 29 CHAPTER IV. LOSSES. To generalise about antediluvian methods of working, about the enormity of ensuing losses, or the obduracy and ignorance of miners and those connected with them, will never make clear the fundamental errors forming the framework of most of the gold-extracting methods in general use. Facts and figures, the reason why, and evidence to support it, must be adduced to prove the truth of every charge against the time-worn customs assailed; therefore, with this course in view, the questions and their answers will be classified as closely as possible, although in the majority of instances the causes of losses are so closely associated and run one into the other that no distinct dividing line can be drawn between them. These losses will be dealt with separately under three heads and do not include problems in alluvial mining : A. FREE MILLING ORES. B. REFRACTORY ORES. C. MERCURY. FREE MILLING ORES are those which yield their gold, when subjected to the processes of crushing, and amalgamating with mercury. REFRACTORY ORES are those which contain "fold in such o association as to cause much loss in the ordinary process of crushing and amalgamating, or where other minerals 30 Losses. are present with gold, which, by 'their physical and chemical properties, act deleteriously on mercury and render amalgamation difficult. A. LOSSES OF GOLD IN FREE MILLING ORES. 1. Fine gold held in suspension by water and carried down stream. 2. Fine gold particles encased or attached to pieces of rock and carried into tailings or down stream. 3. Clayey ores make the battery water very muddy and holds mechanically fine gold particles in sus- pension, until deposited in tailings or down stream. 4i yWhen any artificial conditions arise, whereby certain substances may find their way into crushing mills or other appliances, practically insuperable difficulties may be occasioned; similar results may arise from natural films coating the gold. Anything which creates films and prevents perfect contact between the metals, renders the gold non-amalga- mable, therefore all but the heavier particles will be swept into the tailings or down stream. 5. Though gold be in a perfect condition for amalgama- tion, impure mercury will not act; in such a case, al] but the heavier particles would be washed into tailings or down stream. 6. Though both gold and mercury be in a perfect con- dition for amalgamation, and have amalgamated, excessive stamping in batteries, agitation or grind- ing action in the machinery and other causes bring about granulation of the amalgam and leave it in a condition to be readily carried off by water, either into tailings or down stream. Losses. 31 B. Loss OF GOLD IN REFRACTORY ORES. 1. Fine gold held in suspension by water and carried down stream. 2. Fine gold attached to pieces of rock or encased in pieces of base mineral and carried into tailings or down stream. 3. Base minerals associated with the gold invari- ably coat the surfaces of gold particles to a large percentage of the total quantity contained in the ore, and also give rise to complicated chemical reactions ; the effect of either or both actions is to prevent amalgamation, and allow the gold to be carried into tailings or down stream. 4. The partial decomposition of base minerals in refrac- tory ores produce acidulated water and its train of attendant evils which act deleteriously in amalgamation, causing granulation of the mercury (sickening or flouring) which prevents the particles re-uniting, leaving them in a condition to be readily carried by water ; gold, amalgam, and mercury are then in the best possible condition to be carried off by the water, either into the tailings or down stream. 5. The mechanical effect of heavy mineral particles in the ore, falling through the stream of water, prevent contact between the amalgamating sur- faces and eventually cut off and clean the amalgam and mercury from the plates, causing loss of gold, mercury, and amalgam. Most of the sources of loss enumerated above are common to both classes of ore ; they are not twice specified in every case, in order to reduce repetition. 32 Losses. C. LOSSES OF MERCURY. Continuous stamping, agitation, or grinding causes mercury to form into minute globules ; these have the property of collecting fine films of matter and air particles on their surface, which reduce their relative weights, preventing their reunition, and are thus in a condition to be readily carried off by water into tailings or down stream. o The following record of experiments and observations in actual practice will prove conclusively that the fore- going dangers are not imaginary, nor are they magnified. From every part of the world where gold mining is carried out, the tale is the same, when told by men who investigate the actual condition of things. Under the various heads, already detailed and numbered, the causes of losses will be dealt with in greater detail and the result of experiments given. A 1. Fine gold held in suspension by water and carried down stream. At Spring Gully Mines Thornborough Hodgkinson Goldfield Queensland when dealing with an ordinary clean white gold-bearing quartz, the existence of a con- tinued and regular loss was observed between the actual returns from ore, milled in the ordinary stamper battery, with the crushings, afterwards treated by the most approved amalgamating methods, and the estimated . returns, calculated upon assay values. In order to determine in a practical manner the cause of this loss, the following experiment was carried out : Two five-head batteries, side by side, were fed equally, and at the same time, from a heap of quartz weighing 100 tons, the Losses. 3 3 in both cases being passed over amalgamating plates. In one case it was led into a pit, from which there was the usual and constant stream of water overflowing from the surface ; in the other case, with a similar quantity of water, it was led into a pit of 500-ton capacity, from which no water was allowed to flow from the surface, the surplus having to filter through the pulp and escape from the bottom. In both cases the yield from the ore, of the gold caught in the battery and on the plates, was 1 oz. 10 dwts. per ton. The tailings from both pits were then carefully sampled and assayed : in the first case, where the surface water escaped, the returns were constant to about 7 dwts. per ton ; in the second case, where the water filtered through the pulp or tailings, the returns were constant to about 15 dwts. per ton. This showed a loss of 8 dwts. per ton of gold carried off by water ; over 25 per cent, of the quantity saved by the original treat- ment, in money value a loss of 30s. per ton (roughly).f At the Mount Morgan mine in Queensland, already described, the ore is one generally regarded by mining men as a free milling ore, namely, with an entire absence of such ingredients as sulphur, arsenic, antimony, &c., Although in individually minute particles, the gold was perfectly clean, yet as a matter of fact, it proved as "refractory" and as difficult of treatment as one most highly charged with mineral sulphides or arsenides. J As before stated, the matrix is a silicious brown iron ore varying from nearly pure silica to true limonite ;|| * Crushed rock and metal. t Mr. George Latta, in New South Wales, as far back as 1865, perhaps earlier, followed the same procedure on a small scale in obtaining assay samples. t See result of Dr. Leibius' experiments quoted on page 36. I! Brown iron ore. 34 Losses. stalactitic masses frequently occur. Some of these stalactitic formations were cut across and polished, which showed that they were composed of a number of concentric rings formed by solutions of varying richness ; some of these rings were nearly pure silica, others almost pure limonite, and the clearer rings showed most gold, although in some cases the limonite was extraordinarily , rich. If a piece of this brown iron ore was put into hydrochloric acid and left undisturbed for a few days, the iron would all be dissolved out, and leave as a residue a friable spongy mass, composed of almost pure silica, the same shape and nearly the same size as before, in which bright flakes of gold, like minute fragments of gold leaf, might be seen. If this silica was squeezed in the fingers no grit of any kind could be felt ; it was as though a paste was being squeezed or pressed. In the early attempts to treat this ore great difficulties and losses presented themselves. The contents, by assay returns, varied from 8 oz. to 1 oz. of gold per ton of ore. The ore was milled and amalgamated in the most careful manner in stamper batteries and other machines, and the tailings ground in pans with mercury until they were an im- palpable powder, the very friable nature of the ore render- ing this comparatively easy. The returns after such treat- ment were about 2 oz. to the ton, and the tailings assayed from 5 oz. to 6 oz., and the loss went on until the pro- prietors had accumulated a heap of tailings, say, 20,000 tons, giving by assay about the before-mentioned average. Scarcity of water prevailed in the district ; the hill wherein the mine is situated was especially waterless ; therefore the battery water was used over and over again, it soon became a rusty colour and contained a great quantity of water-borne gold. After all the mud Losses. 35 and slimes had, as much as possible, been removed from the water by settling pits, the engine boilers were fed by water pumped from the dam nearly 500 ft. below the tailing heap. The boilers soon became coated with scale, and mud settled on the bottom; when they were cleaned and the scale treated, a return of gold was obtained equal to 1 1 oz. per ton of scale. On account of the water difficulty dry crushing was introduced ; this was carried on in a closed building. The dust in the building was held in suspension by almost still air, and some which escaped through crevices in the structure and settled on ledges or projections was after- wards collected and assayed, and found in many instances to give a higher value than the average of the ore. Some of this dust was put in a pan and the oxide of iron dissolved by hydrochloric acid, then the gold which it contained could be seen like yellow distemper paint on the bottom of the dish. Vat chlorination, commonly known as the "Plattner" system, was then introduced; treatment by this means was even a greater failure than amalgamation. Parcels of the ore were then shipped to the German Government smelting works, to England, and to metal- lurgists of the highest repute in San Francisco, so that the difficulty might be solved. By smelting, the Germans were able to get adequate returns, but owing to the highly silicious nature of the ore they could only use it in small quantities, when it would flux with other ores, and consequently would guarantee no regular treat- ment in bulk ; the negotiations therefore came to nothing. In England the same result followed, and the investiga- tions in San Francisco did not result in a solution of the difficulty. In a paper read by Dr. Liebius of the Sydney Mint, 36 Losses. before the Royal Society of New South Wales in 1884, the following record is given of his struggle to solve this metallurgical puzzle. Locke, in his work on gold published in 1882, says no gold has yet been found in nature unalloyed with silver. Yet this gold from the Mount Morgan Mine, of which since February last already over 10,000 oz. have been received as retorted gold at the Sydney Mint, is found to be free from silver a minute trace excepted. I have brought some of this retorted gold rolled out very thin to show its toughness. It assays 99.7 per cent, of gold ; the rest is copper, with a trace of iron. Gold assaying 99.7 per cent, is worth 4:1. 4s. 8d. per oz. Gold from the same mine received at the Mint assayed as high as 99.8 per cent. It is, as far as I know, the richest native gold hitherto found. A not less interesting though, less satisfactory fact is this : that only about half the gold is extracted by the ordinary quartz- crushing and amal- gamating machinery. The tailings which are being stored are said to contain as much gold as is saved, and as they will be subjected to treatment at a future date, the result will be highly advantageous to the owners. Having the small quartz-crushing machinery erected at the Sydney Mint under my charge, I have had an opportunity of test- ing this fact. In November last (1883) we received through Mr. Hall, of Sydney, 458 Ib. of this ferruginous quartz, part of it consisting of picked stone. It was carefully crushed and amalgamated in the Chilian mill with 240 Ib. mercury. Thus 7.44 oz. of gold assaying 991.5 were extracted. Another lot weighing 174 Ib. was similarly treated and 12.12 oz. of gold extracted, assaying 998.2. Thus lot No. 1 gave gold at the rate of 39.32 oz. standard per ton of quartz, while lot No. 2 gave gold at the rate of 169.86 standard per ton of quartz. In lot No. 1 at the rate of 46 oz. 2 dwts. 12 grs. per ton was left in the tailings, while in lot 2 the tailings assayed 64 oz. 5 dwts. 18 grs. of gold per ton. Both lots of tailings were now mixed and passed for two or three hours in the Chilian mill with 240 Ib. clean retorted mercury. Only 1.66 ozs. of gold, assaying 981, were, however, obtained by this treatment. The tailings were dried and found to weigh 476 Ib., containing gold at the rate of 41 oz. 13 dwts. 16 grs. per ton or, in about 476 Ib. tailings no less than 8 oz. 17 dwts. 3 grs. of gold. I have brought some of those tailings here. Under the microscope there is no gold visible. I thought that if the oxide of iron were removed, by boiling the tailings in hydrochloric acid, and the solution filtered off, the gold might more readily be discernible in the boiled-out residue. I found, however, that this was not the case, and that 1000 grains of tailings thus boiled in Losses. 37 strong hydrochloric acid, by which about 20 per cent, were dissolved, gave me only 0.73 grains of gold, the same as when boiled with nitric acid. The loss of gold by boiling in hydrochloric acid, was no doubt due to the action of this acid upon manganese in the ore, whereby chlorine gas was formed, a ready solvent for gold. That the ordinary amalgamating Chilian mill did not extract all the gold in this stone, I can only attribute to the supposition that the oxide of iron has literally coated some of the fine gold, thus preventing it coming in contact with the mercury. In touching upon the action of chlorine it is astonishing to find how close Dr. Liebius got to the ultimate solution of the question before giving the matter up as a bad job. As a last resource, when the " practical man " of Australia proved a failure as, indeed, he usually does in all countries when difficult problems arise some of the ore was sent to the Technological Museum, Mel- bourne, which, in the Colonies by those not too proud to ask for information at home, is regarded as the practical encyclopedia for all scientific questions. Mr. J. Cosmo Newbery, the chief of the institution, examined it, and in his experiments was assisted by Mr. Claude Vautin, who was there working some other experiments at the time. After trying chlorination and the most accurate of known amalgamating methods, that of boiling slimes in a cauldron with mercury both of which processes resulted in failure a very critical examination was made of the nature of the ore. It was then found to be, even when divided into the most impalpable dust, a hydrous oxide of iron* with hydrous silica. t When de-hydrated by heat, the grains became more friable and gave up most of their gold to ordinary amalgamation, the tailings assaying only from 10 dwts. to 20 dwts. per ton, instead of from 5 oz. to 6 oz. of gold as before. When * A combination of iron rust and water, t A combination of water and silica. 38 Losses. the de-hydrated ore was subject to the ordinary vat, or " Plattner " chlorination, the extraction was practically perfect, the quantity left in being only 2 or 3 grains to the ton. So far all was well, but a difficulty arose from the nature of the ore which necessitated the abandonment of the " Plattner " process. The ore being so friable, an enormous proportion of slime was produced by the crushing mills which prevented almost entirely the permeation of chlorine gas and rendered filtration practically impossible; this subsequently led to a modified method now known as the Newbery-Vautin chlorination process. A peculiar feature in the roasting of this ore was noticeable, namely : if some finely ground dry ore was placed in a pan and heated, it soon began to bubble just as boiling water, and an innumerable number of small volcano-like cones were formed by the de-hydra- tion ; if this pan was knocked or tilted ever so little, the whole mass became quick and ran like water into the fire almost instantly. This property rendered the calcination of the slimes and finely crushed ore a matter of extreme difficulty in the ordinary furnace. This class of ore is by no means rare; it is in fact an ironstone gossan, and the ores forming the outcrop of almost every lode, wherein pyrites have decomposed, are gossans of a more or less similar nature. The chief peculiarity of the Mount Morgan Mine is the extraordi- nary richness of the ore and so far undeterminable mag- nitude of the deposit, also the somewhat exceptionally pasty nature of the silica residue, before noticed. As an illustration of how minutely divided water-borne gold, and silica, occur in the waters of almost all mines, certain experiments which were carried out by Mr. J. Cosmo Newbery, chief of the Technological Museum, Losses. 39 Melbourne, throw considerable light on the matter : Mr. Newbery was examining mine timbers which had long been saturated by mine waters, expecting to find in the fibres of the timber, gold, which had been precipitated from solutions ; its soluble condition being brought about by reactions caused by the decomposition of certain salts held by mine waters as before explained.* Some large logs of undressed close-grained eucalyptus timber, which had been in mine waters between twelve and fourteen years, were experimented upon, the outsides of these were cut away and perfectly sound pieces were obtained ; these were dressed quite smooth and to all appearance were as ordinary pieces of planed timber. They were then carefully calcined and the ash examined ; a consider- able quantity of highly minute gold, and silica, being found. Microscopical examination of these showed that both gold and silica were in rough and irregular particles, quite unlike the forms they would have assumed had they been there precipitated from solutions ; the capillary attraction of the wood had drawn them amongst the fibres together with the water. In carrying these ex- periments further Mr. Newbery endeavoured to obtain mine waters from which all matter held in suspension had been filtered, so as to test for metals held in solution. For this purpose he passed mine waters through a felt filter, such as is used by chemists ; even after this he found that impalpably minute metallic gold had passed with the water through the pores of this filter. At Sandhurst, Victoria, the customs mills crush what are usually considered free milling ores, namely, ordinary quartz with about 2 per cent, of concentrates ; the drain- age from the mills run into a creek. The tailings at the * Properties, pages 8-10. 40 Losses. batteries give, by assay, an average return of about 4 dwts. to the ton. As lias been already explained, slimes, -are the fine water-borne portions of the ore. Some of the slimes had been carried by the water for miles down the creek, and concentrated in places by the natural ripples and eddies in the water ; some small patches were obtained three miles below the batteries which returned by assay 18 dwts. of gold to the ton of concentrated slimes. Mr. Edward Dunn, geologist to the Cape Government, brought to the Melbourne Technological Museum some gold which he had collected in South Africa from the rock called " banket." The gold was in a brown dust, the grains of which were so fine as only to be distinguish- able under a microscope of high power. When thrown on a close-grained white paper the dust discoloured the paper with a brown stain ; this examined by the micro- scope proved to be minute gold particles caught in the fibres of the paper. A small quantity of this' brown powder put in a test tube with distilled water and shaken up, gave a distinct purple colour to the water with trans- mitted light, and light green with reflected light ; a considerable time elapsed before the metal deposited and the water resumed its natural colour. It may be here noted that any illustrations given of the finely divided condition of gold are only in proof of its common occurrence in nature in such a form. That metallic gold exists in a still more infinitely fine condition is indisputable, and may be easily demonstrated by solutions permanently coloured by fine gold which give no sediment or deposit. In an official publication of the United States Losses. 41 Government^ the following tests by Mr. G. McDougal, of Grass Valley, California, are given as evidence of loss by water-borne gold ; the experiments were regarding two mills situated in that locality. From water flowing three-quarters of a mile below mills : Cents. 1st test of 20 gallons of water gave gold to the value of 1.10 2nd 2.13 3rd ,, .95 4th ,, ,, .83 5th 1.02 6th ,, ,, 1.13 ^th ,, 55 55 55 55 " I 8th 3.12 9th ; 1.07 10th 55 5, .63 llth 1.01 12th ,, -90 Average 1.18 It was estimated that 576,000 gallons of this muddy water flowed by every twenty-four hours, which, according to these testa, contains 339.84 dols. Let us carry this calculation a little further. The average amount of ore worked in twenty-four hours was given at 58 tons ; this shows that 5.85 dols. float, which probably is 20 per cent, of the yield. Let us carry the loss a little further. Suppose that the two mills run 250 days in each year, which is not unreasonable, and we have a yearly loss of float gold alone, to say nothing of loss by imperfect pulverisation and general wastage, of 84,960 dols. from two mills. From the same source as the above, the writings of Mr. Almarin B. Paul, of San Francisco, may be quoted : A friend of mine, having somewhat similar ideas to my own, con eluded to test the question of float gold as well as he could at the time and embraced the opportunity of cleaning up the slum from a water * " Statistics of Mines and Mining in the United States and Terri- tories West of the Rocky Mountains," by Rossi ter W. Raymond, United States Commissioner of Mining Statistics. 42 Losses. tank for supplying the battery, where the water was used over and over again in consequence of its scarcity. The ores were worked after the usual wet methods for gold ores. The water and pulp were first passed through a sluice to a tailing bed, 190 ft. The tailings being deposited the water was drawn off at the top, flowing into a well where it was raised and passed through a sluice 120 ft. to tank at battery. This is the tank cleaned up. The residue was amalgamated in a tub quite rudely, but with a large body of mercury and chemicals, the result was 33 dols. in silver and 56 dols. in gold, making a total of 89 dols. per ton. It will be observed there were two chances for the metal to precipitate previous to reaching this tank ; first in the tailing reservoir and second in the well. In another part of the same article Mr. Paul continues : Our present general system of gold mining is based upon the idea that gold is mainly coarse, while examination will show that the high percentage is in atoms finer than flour itself. In my experiments gold has been taken up so fine that in distilled water it would not precipitate in less than from five to ten minutes. Can you save gold of this kind by running it down stream 1 Gold in quartz, of gravity enough to resist the pressure of any stream of water is the exception, and this is the aggregation of the finer particles, the primary simple condition, in my opinion being flour or powder of gold. It is the flour of gold we must seek to obtain, to get the wealth of our ores. Engineering, of the 26th August, 1887, referring to Australian practice, says : A mining manager in estimating his loss of gold, generally assays his tailings or refuse and counts the loss to be what is found there, utterly ignoring the large percentage which is swept off by water and disappears Water that has flowed through the battery and deposited tailings in various receptacles, until apparently quite clear and pure, has been caught in a dam and the fine sediment deposited there experimented on and gold of an extreme fineness found. One writer says : ' I have collected some of this gold, which, when shaken in a bottle of distilled water, is scarcely visible; it colours the water a light purple tint, and remains suspended for a long time ; it seems the friction of the gold particles with the water is powerful enough to nearly neutralise the high specific gravity of the gold.' It will be seen that the strong current flowing through the battery carries away much of the fine gold, over the tailing heaps, and deposits it far Losses. 43 and wide down the creek, where no one thinks of looking for it, and even if they did, the difficulty of collection would be excessive. Though not dealing with alluvial or hydraulic mining, it is of interest to note that this exceedingly fine gold occurs in alluvial deposits, and that some of it is capable of being saved by simple mechanical means. The placer mines of the southern counties of California have been regularly worked of late years, except where there was an insufficiency of water. In the winter season, when there is an abundance of water, the miners have lately learned to save the ' float gold,' a nearly im- palpable dust which floats on the surface of the water. The method adopted is quite simple, consisting of a series of weirs placed across the stream, so that water shall flow over each in succession. These weirs are constructed of piles and timber with coarse gunny cloth covering the upper side. In rainy seasons, in a rich gold-bearing canon, what extra is saved by the weirs is estimated at from 10 dols. to 30 dols. per week, according to the richness of the dirt above and the number of weirs. In any case they are profitable, as their cost is small.* In Victoria, Chinamen make a good living by boiling the sludges from alluvial mining, in iron pots, with mercury and water. A 2. Fine Gold Particles Encased or Attached to Pieces of Rock and Carried into Tailings or Down Stream. It will no doubt be apparent to those who read the notes under head A 1, that no such thing as a distinct line exists between the losses under the former head and the one now being dealt with ; the present is simply a coarser condition of ore residues, one more generally known and more easily demonstrated than the first. The following observations and experiments being more strictly confined to what are commonly known as tailings a coarser condition than slime residues will serve as practical illustrations of the loss. * "Production of Precious Metals in the United States," 1883, by Walter A. Skidmore, page 722. 44 Losses. The following tests were carried out in California and are recorded by Mr. Paul in the article previously referred to under head A 1. Test No. 1. Average yield of ore in mill 18.60 dols. per ton. Wastage after complete washing including concentration ; silver, 3.14 dols. ; gold, 10.04 dols. ; total, 13.18 dols. per ton. Test No. 2. Same mill tailings 350 ft. from mill. Silver, 3.93 dols. ; gold, 5.02 dols. total, 8.98 dols. per ton. Showing that a portion secreted itself in passage down stream. Test No. 3. Average yield of 150 tons, 3.50 dols. per ton. Assay of tailings (from above ore) carefully sampled. Silver, 6. 28 dols. ; gold, 13.55 dols. ; total, 18.83 dols. loss per ton. Silver, 6.28 dols. ; gold, 8.79 dols. ; total, 15.07 dols. loss per ton. The above bad results were occasioned by the extreme fineness of the gold, and the above does show the full wastage. In another portion of the article is the following : I made a test of 50 Ib. of tailings for a party who took them a mile below his mill, and the return was 55 per cent, of what was his average working. I also made a test of three-quarters of a ton, and the result showed the loss in the mill working to be 63 per cent. From what attention I have given the subject in actual labour, as well as collecting all the data attainable in others, I know that the loss as a whole is fully 50 per cent., and in the majority of mills all of 60 per cent, of what the ore contains One step in advance would be, taking more care. There is too much slashing about in our gold mining .... This plan of seeing how much can be pounded up and rushed through in twenty-four hours is a false, wasteful, and ruinous system It is too universal to consider that it is only necessary to rig up a set of stamps, apply the power, and let them rip away, smashing rocks to wash over blankets and copper plates ; and all is done with a stream of water to wash the sand off, forgetting that it is equally as potent to wash off the smaller particles of gold. A 3. Clayey ores make the battery water very muddy which holds mechanically fine gold particles in sus- pension until deposited in tailings or down stream. When an ore is clayey and makes muddy water, a large percentage of the gold is carried away in suspension by the battery water. These gold particles are not necessarily Losses. 45 coated by mud, attached to, or contained in its particles, but are kept afloat by the mechanical action of the mud. If the quantity of water sent through the battery is reduced so as to give the gold time to settle, the mud also settles and covers the surfaces of the plates and prevents amalgamation ; an increase of water frequently washes everything away. In such a case the usual remedy is to feed into the battery, together with the ore, a quantity of hard material, so as to reduce the proportion of clay to the crushed mass passing off with the water ; this means a highly increased cost of treatment, caused by obtaining, handling, and crushing barren and worthless material. Mr. Deetken, of Grass Valley, California, gives as the result of his investigations,^ that Battery sands passing through a No. 6 slot screen (25 mesh) con- tain 19 per cent, of slimes which remain suspended in still water after three minutes' rest. To obtain even this result the ores which came under Mr. Deetken's observation must have been especially good settling ores. A 4. When any artificial conditions arise whereby certain substances may find their way into crushing mills or other appliances, practically insuperable difficulties may be occasioned; similar results may arise from natural films coating the gold. Any- thing which creates films and prevents perfect contact between the metals, renders the gold non- amalgamable, therefore all but the heavier particles will be swept into the tailings or down stream. In cases where water is scarce, much of it is frequently * " Statistics of Mines and Mining in the States and Territories West of Rocky Mountains." 46 Losses. obtained from the mine pumpings, which are always more or less saline, and it is used over and over again to carry . the ore through the battery; it flows over tailing heaps and into pits to deposit slimes, from whence it is pumped back to the battery, therefore it is continually coming into contact with crushed ore which has been exposed to atmospheric action. Very many ores contain one or two per cent, of sulphurets, a quantity not sufficient to remove them from the class of free milling ores ; these crushed sulphurets rapidly decompose when exposed to the atmosphere, and sulphuric acid is produced, which is dissolved by the water ; the more often the water per- colates through the heaps of crushed ore, the more heavily does it become charged with sulphuric acid and acid sulphates. When this acidulated water is used in a battery many complicated reactions may take place. As an illustration the case of a ship's propeller may be cited. It is well known that when a gun- metal propeller is fixed in an iron ship, without being properly insulated, and run in salt water, a galvanic action is set up between the ship and the pro- peller, so that the stern-post and ship's bottom rapidly corrode and waste away. In like manner, if an iron stamper battery with copper plates be run empty, and at the same time acidulated waters be passed through, it is at once converted into a galvanic battery ; if, while in this condition a number of other substances contained in the ore are introduced, a fresh set of actions are set up; these produce re-actions and so on, until the chemical changes taking place inside the battery boxes become very highly complex and to the average miner absolutely inexplicable; though a worker may understand thoroughly all the individual actions, there are few who can follow Losses. 47 these endless combinations and their detrimental effect in rendering gold non-amalgamable. It is from the corrosive action set up in the manner explained, together with the peculiar molecular change produced by acid saline waters to be noted hereafter that gratings so frequently burst, flood the plates, and cause all kinds of trouble to the millman. The formation of films, and other causes which pre- vent amalgamation, may be accounted for by the presence in the stamper battery or other appliance, of certain soapy varieties of powdered hydrated silicates of magnesia, or alumina, grease, urine, decomposing animal or vegetable matter contained in impure water, or water impregnated with sulphuretted hydrogen, or containing certain soluble metallic salts. Excessive hammering from stamp action, air globules adhering to minute gold particles, and other causes, renders gold non-amalga- mable, but the effect of some of the substances noted are most felt in amalgamators. Mr. William Skey, the analyst to the Geological Sur- vey of New Zealand, when writing on the reported loss of gold on the Thames field, gives the following as the result of his researches : That numerous samples of bright clean gold of all degrees of fineness, refuse to amalgamate on any part of their natural surfaces though taken direct from the reef and untouched by hand. That on such surfaces sulphur is always present. That native gold, or gold in a pure state, readily absorbs sulphur from moist sulphuretted hydrogen or sulphide of ammonium. . . . That surfaces so affected refuse to amalgamate though no apparent change can be observed in their aspect. The action of sulphuretted hydrogen upon gold in rendering it non- amalgamable when placed in contact with mercury was demonstrated with striking effect by the author. From these results the author has been led to suppose that a large area of the natural surfaces of native 48 Losses. gold is covered with a thin film of an auriferous sulphide, and that the greater part of the gold which escapes amalgamation at the battery is represented by that portion of this sulphurised gold which has remained unabraded during the process of milling or extraction from the reef ; the state of the gold, rather than that of the mercury, therefore, being the greatest impediment to thorough amalgamation. That this absorption is altogether of a chemical nature. In ores where acidulated water is not in itself sufficient to produce sulphuretted hydrogen, the galvanic action before mentioned will, when set up, at once bring about the production of the gas in places where it can most readily exert its influence on the gold. Referring to the causes preventing gold amalgamating,. Professor Egleston, Ph. X)., School of Mines, New York City, writes as follows :* In order to ascertain the causes which prevent the amalgamation of gold, I undertook to reproduce artificially the conditions which were supposed to prevent it. These I found to be mechanical and chemical. I found that if a piece of soft gold, which could be easily bent and amalgamated readily, was hammered on a perfectly bright anvil with a bright hammer, given several rapid blows until the gold had become hard, and had acquired a certain amount of elasticity, it would remain in juxtaposition with mercury for a very long time without being affected by it. This hammering increases the density of the metal and closes the pores, so that I have recently had a piece of gold, which was put into this condition by hammering, remain nearly two weeks floating on the mercury without being attacked. If gold in this condition is heated and cooled slowly, it again amalgamates rapidly. If, however, it is cooled rapidly by plunging it suddenly into very cold water, the amalgamation takes place very slowly. The metal, after being repeatedly rapidly cooled and heated, amalgamates more readily than if it has only been treated onoe. .... The effects of grease are well known, and the greatest care is taken in most mills to keep the ' quick't bright, either by rubbing or by the addition of chemicals, to such an exent in some cases, that the chemical themselves, used in excess, are often a cause of the very thing * Transactions American Institute of Mining Engineers, vol. ix.,, page 633. f Mercury and amalgam. Losses. 49 they are intended to prevent. All these causes, the hammering, the effect of sulphuretted waters, and also the effect of grease, occur in every mill, and probably have something to do with the losses of gold which take place there. It will thus be seen that the stamp mill is not a rationally designed machine. The action of the pounding is likely to put some of the gold into such a condition that mercury will not touch it, and to flour the gold as well as the quicksilver. There is, besides, in the mill every probability of the introduction of grease or greasy substances, like the powdered hydrated silicates of magnesia and of alumina, which not only froth but coat the gold with a slime which prevents the action of the mercury. If the water used in the mill is not pure, there is a fur- ther likelihood of the introduction of sulphuretted hydrogen, and of other soluble sulphides, which act superficially on small particles of gold and prevent the action of the mercury. A 5. Though gold be in a perfect condition for amal- gamation, impure mercury will not act ; in such a case all but the heavier gold particles would be washed into tailings or down stream. This is one of the points brought daily under the notice of millmen in any reduction works. Careful workers will guard against the introduction of grease and many other substances which act deleteriously on mercury ; but there are cases where the mercury becoming foul in boxes, in ripples, and on the plates, defies all like pre- cautions. One of the principal causes, especially where the trouble is found with amalgamated plates, no doubt results from the action of saline and acidulated waters, already explained. In any case, if thoroughly investi- gated, the objectionable influence may be traced, provided the worker has sufficient chemical knowledge, and in such a case a remedy can doubtless be applied. This cause of loss and those under head A 4 are so closely allied that it is almost impossible to say where one ends and the other begins. 50 Losses. A 6. Though gold and mercury be in a perfect condi- tion for amalgamation, and have amalgamated^ excessive stamping in batteries, agitation, or grind- ing in machinery, and other causes, bring about granulation of the amalgam and leave it in a con- dition to be readily carried off by water, either into tailings or down stream. The action of a falling stamp, or a grinding-pan, breaks mercury up into small particles which assume a globular form. If perfectly clean mercury were broken up by a perfectly clean practically infriable machine, doubtless, no amount of grinding would prevent the particles reuniting, unless air globules or finely powdered foreign substances were present which could coat the particles. In stamp mills and grinding pans the wear of metal is very heavy, it is continually coming away in very minute particles ; excessive stamping or grinding also produces minute ore particles. The shining surfaces of the mer- cury rapidly become coated therewith, and films are con- sequently created which prevent the globules reuniting; the longer any material and mercury are together subject to the action of machinery, the more likelihood there is of loss accruing. When treating a free milling ore in a well-managed and regulated plant, if the loss of amalgam is great, close investigation will frequently reveal a special cause, such as the action of some heavy mineral contained in the ore; the presence of heavy spar, scoro- dite, &c., or like substance may not be noticed, owing to similarity in colour to the ore, until, on the stripping of the plates, the manager looks for the cause of the loss. Rossiter W. Raymond, when United States Commis- sioner of Mining Statistics, wrote as follows :* * Raymond's reports, 1870. Losses. 51 Floured or granulated quicksilver, or fine particles of gold, have in common with some other polished metals the property of condensing on their surface films of air which decrease the specific gravity of particle. As the amount of air, hence the amount of decrease in specific is pro- portional to the surface exposed, and its ratio to the mass of the par- ticle ; and as the smallest particles expose always the largest propor- tional surfaces (the cube roots of the volumes being as the square roots of the surfaces), it follows that very fine particles will acquire a density less than of water, and will in fact float upon it. Many more will be rendered so light as to settle very slowly. Mr. Charles G. Yale, writing in the official publication of the United States Government " Precious Metals in the United States/' states : * Swinging plates for float gold are now in use in many places in California, and in other gold regions on the Pacific coast. They are all adapted for use in the sluice below the battery of a quartz mill or in sluices in any position where there is not too great a flow of water or material. The swinging plate consists of a curved strip of silver-plated amalgamated plate, about 3 in. deep, and the width of the sluice or flume in which it is to be used. It is swung on eyes, through which passes a wire rod resting on the edges of the sluice. The plate thus hangs transversely to the current, with its concave face up stream, the plate being half submerged. The movement of the water will keep the plate swinging. The floating particles of gold cannot escape touching the plate, and are caught on the quicksilver surface. It is found in practice that across the sluice, immediately under each swinging plate, is formed a line of amalgam, which has dropped from the plate as it accumulated. The gold which is caught on the plate is thus saved. These plates are hung in sluices a few feet apart. Very wide ones have been made for the sluices of hydraulic mines. The plates cost so very little and are so effective that they have come into extensive use. They are silver-plated, the same as the ordinary plates in use in quartz mills. Although the foregoing is a most practical proof of the existence of floating gold and amalgam, yet, as a matter of fact, it is only likely to save a very small pro- portion of the total quantity carried away, and most of * 1881. 52 Losses. the floating gold and amalgam do escape contact with the amalgamated plate. The action of water when flowing under any obstruction is so well known that it need not be entered upon, save to point out, that a cushion of comparatively still water is always imposed between the flowing current and the obstruction and it is against the outer portions of this cushion that the large proportion of floating substances would strike. In concluding these notes and references to the great losses occasioned by many causes in the so-called " free milling ores," the following from the pen of Mr. J. R. Hardenberg* should be -learned as an article of faith by all gold miners, and every one, speculator or otherwise, who has any connection with the industry. .... The simple truth is that since the beginning of quartz mining in California, those who have engaged in it have been misled or have misled themselves by the fallacy involVed in miners ignis fatuuS) covered by the hackneyed experience of the milling ores. As a rule the whole of the quartz mining in California until a very recent period has been carried on upon the basis of the " f ree milling" pro- position, meaning mining, crushing, pulverising, and extracting gold by the amalgamating process, and regardless of the fact that the per- centage of gold contained in pulp, capable of being caught and retained by the agency of quicksilver in whatever form it may have been used, has been but a fraction of the assay value of the whole mass, while larger proportions have as regularly gone to waste as the water has flowed from the batteries in which the ore has been treated. The result achieved, therefore, from the working of these ores has been but a small part of the assay value, which has, in the main, only served as a " will-o'-the-wisp " to lead capital and human energy to merciless wreck and ruin. In spite of all this, in spite of years of costly and destructive experience, men have persistently continued to engage in mining enterprises to be carried on in the old manner, and to result in the continued accumulation of abandoned monuments of lost capital and stranded human hopes. * Writing on California, in the official publication of the United States Government " Precious Metals in the United States, 1882." Losses. 53 The free milling manner, while it has, despite the fallacy which it involves, helped largely to swell the yearly aggregate of California's, gold product, by reason of its inadequacy and utter inefficiency has visibly retarded her mineral development, and kept her yearly gold product far, very far, below the figure that her natural resources and the natural energy of her people call for. It has taken long years and the sacrifice of many hundreds of thousands of dollars to clearly demonstrate this fallacy, but miners and mining men have pursued the phantom with a determination bordering on self-destruction rather than to abandon the free milling madness and the solace afforded for disasters by the rebellious ore theory. The simple truth is that the wealth, the next to inexhaustible gold wealth of California, lies in the so-called rebellious ores themselves, which are in no sense rebellious other than that the gold which they contain cannot be extracted by any known free-milling amalgamating process, any more than roast beef can be converted into chicken soup, or flesh into fish. .... Enough to say that all authorities, and they might be quoted to endless length, agree that such losses constantly occur under the system of gold mining which has heretofore prevailed ; and to add as the necessary corollary, that this system has been, almost exclusively, the stamp mill and amalgamation, in one form or another, or, to return to our tough matter, "free milling." B. LOSS OF GOLD IN REFRACTORY ORES. The general methods adopted for treating " refractory ores " have followed so closely the ordinary procedure for working "free-milling ores" that very many of the causes of loss will be identical with those previously enumerated. B 1. Fine gold held in suspension by water and carried down stream. The causes bringing about this loss are almost identical with those mentioned under head A 1 , but with ores called '''refractory" or "rebellious" the difficulty, inmost cases, is likely to become more acute. In all metallurgical operations where ores are crushed 54 Losses. so as to liberate the mineral from its enveloping gangue, and these crushings subsequently treated by a stream of water, the formation of slimes so easily carried away is the greatest source of loss. As a rule the portions of the ore containing the largest quantity of mineral are by far the most brittle. As in most crushing operations the whole body of ore is reduced until it is sufficiently small to pass through a particular screen. The operation neces- sary to reduce the gangue to this condition must be continued long after the mineral portions are of the required size, and as all together are subject to the action of machinery, the reduction of a large proportion of mineral to an impalpable powder follows as a natural consequence the process of reducing its hard enveloping matrix to screen sizes. In a great many cases these minerals are distributed through the matrix in individual pieces sufficiently small to pass through the screens pro- vided for the purpose of regulating this size. In such a case they simply require liberating, yet the operation of doing so invariably results in bringing a large proportion of them to such a degree of fineness that they become a positive impediment to metallurgical operations as well as a source of great loss of metal. With ores holding metallic sulphides, &c., in large lumps, the result is the same owing to the crystalline and friable structure of such metallic bodies. As a simple demonstration of the foregoing: take an ore containing metallic sulphides, rub it with the fingers or a piece of white cloth or paper, and examine with a microscope the resulting stain, it will be found to consist of a number of minute metal lie grains; where decomposition is going on the result is more plainly seen. Another method, and one which follows the principles generally adopted in Losses. 55 treating ores, is : Put a piece of mineralised ore into an ordinary mortar and give it a few blows and turns with a pestle, the result will be a few lumps of ore and gangue, a proportion of sand-like sizes, and also a quantity of fine dust. Throw half of this into a long glass test tube, a large proportion of the stones and metal will sink to the bottom at once, the sand will settle slowly, the dust very slowly, and in most cases the water will be discoloured ; this dis- coloration is caused by particles of mineral too minute to be discerned by the unaided eye, which are held in suspension by water. Then treat the other half in the mortar until reduced to sizes common in the treatment of gold ores, say ^th of an inch in diameter 40-mesh screen then throw these crushings into another test tube, and observe the result ; most frequently the water will be highly discoloured and remain so for days, and the crushings will find their way to the bottom according to their relative weights which, broadly speak- ing, is more governed by size than density. If this discoloured water be poured off and allowed time to settle, the sediment would give a far higher return ot metal than the coarser portions of the ore which fall to the bottom quickly. Such sediments compose the " slimes " which unfortu- nately in the majority of mills are considered as unat- tractive, objectionable, and valueless, as their name would imply, and are accordingly got rid of with the greatest possible celerity. The following extracts from a paper read by Mr. George Latta before the Royal Society of New South Wales throw considerable light on the condition of gold when associated with refractory ores. In reference to the condition of gold in pyrites it has come to be 56 Losses. pretty generally admitted that ' nearly, if not quite, all the gold exists in the metallic state.' This quite agrees with the results of some experiments carried out by myself in conjunction with Mr. Daintree, late of the Victorian geological staff. Our researches ended in our obtaining but the barest possible evidence of gold existing in a mineralised state in pyrites. As a matter bearing somewhat in support of this result, and whilst engaged in these investigations, I had the good fortune to come across some good specimens of cubical pyrites, which upon examination with a pocket lens, seemed to indicate the presence of gold ; upon transferring them to a good microscope, gold was distinctly seen upon the planes of cleavage, and upon dissecting the crystals every cleavage face was found distinctly gilded. Now from the fact that the presence of gold could only be determined by the aid of a good microscope, and that only as a fine gilding, some notion may be formed of the excessively fine state of its division, and how unsatisfactory would be the task of separating such liberated films from water in motion. Guided by these considerations it became evident that any attempt to mechanically separate gold from pyrite unless aided by the previous decomposition of its enveloping sulphides must prove ineffectual from the impossibility of reducing it to its ultimate atoms, for so long as a cluster of sulphide atoms remain unbroken, they might reasonably be imagined to contain those of gold. Again it was equally clear that when such gold was liberated from its envelope, water concentration alone was inapplicable. To test the correctness of these conclusions, each of them was made a subject of rigid examination, over an extended scale, before receiving them as fundamental truths to guide us in deter- mining the best methods suitable to our requirements. Two parcels of pyrites, 20 tons each one roasted, the other unroasted were ground, in one of the best arrastras known, with mercury ; a constant stream of water flowing through to carry off the finely -ground sand, which was then carried through mercury boxes and over blankets. Each parcel receives the same amount of grinding and treatment in every detail ; the result is as follows : 20 tons raw sand containing 3 oz. 6 dwts. per ton. Gold obtained . . . . . .29.21 per cent. left in tailings 42.84 ,, carried off in water .... 27.95 20 tons roasted sand containing 1 oz. 7 dwts. 10 grs. per ton. Gold obtained . . . . . .51.75 per cent. left in tailings 27.21 carried off by water .... 21.22 Losses. 57 Here it will be observed that with the raw sand only a small portion of the gold was obtained, a very much larger was left in the tailings although finely ground, and a large proportion was carried off by the water as slime. With the roasted mineral more than half the gold was obtained ; the tailings were very much poorer than those from the raw sand, but still very rich, and a large quantity was carried off by water. Mr. Latta then describes the various methods sug- gested to destroy the pyrite envelope ; eventually it was decided to roast all the pyrites (a parcel of 294 tons) and grind in a Chilian mill for about three-quarters of an hour equal weights of damped ore and mercury practically the ancient amalgamating method of the Mexicans and South Americans, used chiefly in treating silver ores. After the ore and mercury were thoroughly ground and intermixed, water was introduced and the mill set revolving slowly until puddle was formed. A continuous stream of water was then run in while the mill revolved until all the tailings sands were carried off. These were twice concentrated in " buddies " to save the fine amalgam lost from the Chilian mill ; efforts were made to curtail the amount of grinding, for the purpose of reducing the loss in mercury, but whenever grinding was lessened a heavy loss of gold resulted. Mercury to the extent of 1 Ib. 13 oz. was lost in treating one ton of ore, or a total of 533 Ib., worth about 90/. The cost of treatment, not including interest on capital, cost and wear and tear of machinery, was equal to 2l. 2s. 4d. per ton, a total of 622Z. 6s. The gold saved by the process amounted to 95.19 of assay values, but for individual lots as high returns as 98 per cent, were obtained. The return of gold is given at 4^ oz. per ton (value not stated), therefore the total quantity lost was worth about 235/. Satisfactory as the percentage saved appears to be, more correct modern methods would 58 Losses. have resulted in the saving of about 530/. in treating this small parcel of 294 tons; the sum would be considerably increased if the very heavy cost of wear and tear of machinery had been included. At the Walhalla Mine in Victoria, Mr. Henry Rosales has worked for many years in a somewhat similar fashion, and has obtained almost the assay values of his concen- trates. Unroasted concentrates are ground and amalga- mated in Hungarian mills fixed in series, and by this means better results are obtained than by the more ordi- nary methods of calcination and amalgamation. A simple statement to this effect may be misleading, but without a more intimate knowledge of the details of Mr. Resales' workings it is impossible to say whether a loss was not brought about by the manner in which the roasting operations were conducted. At all events, it is well known that improper roasting or hurrying the process always results in very great losses of gold. In the par- ticular case under notice there were unusual conditions present to bring about satisfactory results : a surplus of battery engine power, utilised in driving the Hungarian mills ; the quantity of concentrates not exceeding ten tons monthly ; the whole month available for their treat- ment ; and the individual care and attention devoted, unusual to a marked degree. Although the foregoing method was so adaptable at the Walhalla Mine, when tried on the concentrates of the adjoining mine the Long Tunnel it entirely failed to produce satisfactory results. In reference to the question of gold-bearing pyritous ores, Mr. Melville Atwood, in a paper prepared for the State Mining Bureau of California,* referring to Mr. Latta's researches, writes as follows : * "Precious Metals in the United States," 1881. Losses. 59 It is now generally admitted by metallurgists of any note that gold in pyrites exists in a metallic state. It is with no little pleasure I am enabled to practically corroborate the statements of Mr. Latta on the subject, having produced for your inspection a number of crystals and fragments of crystals of auriferous pyrites obtained from different parts of this state. They are mounted on glass slides for microscopic exami- nation, as with a common lens the presence of gold can hardly be detected, but with a good microscope, using a 1 in. or ^ in. objective, it will be found that the faces of some of the crystals are, in places, most finely and beautifully gilded, and that here and there are seen little specks or drops of gold, partially imbedded in the pyrite. The mill-man looking at these specimens will not be surprised at the loss sustained in the wet stamping of auriferous pyrites. B 2. Fine gold attached to pieces of rock, or encased in pieces of base minerals, and carried into tailings. The notes under head B 1 practically comprise the answer to this inquiry, but the following experiment gives answer to a problem which often appears inexplicable to miners and others working with auriferous pyritous ores. It has many a time been noticed that certain gold- bearing pyrites, when roasted, then crushed and subjected to a stream of water, or washing, leave a residue of fine gold particles behind when all other crushed matter is washed off, and that if a portion of this same pyrites be crushed, without roasting, no gold of any description can be seen after similar washing. In order to throw some light on the phenomenon the following tests were insti- tuted : In the Walhalla district, Victoria, certain pyrites in the bed of a creek gave by assay the return of 150 oz. of gold to a ton. When these pyrites were crushed no gold was visible to the unaided eye, though after roasting, they were found to be full of small gold specks. Several cubes of pyrites were obtained, which had passed 60 Losses. through a 30-mesh screen ; these were carefully examined and no trace of gold was discernible, even when using a powerful microscope. Several cubes were placed on the tablet of a microscope, and a 1-inch objective used ; they were then subjected to a blowpipe oxidising flame, and the process of oxidation was observed microscopically. The exfoliation of the cubes was clearly seen during the decomposition of the pyrites, and the residue of oxide of iron assumed a spongy condition, showing minute threads and films of gold interwoven. As the oxidation was proceeded with, and the temperature increased, the threads and films could be seen gradually drawing together, until they formed one little speck of gold. The experiment would point to the same natural process as that taken advantage of in the kernel roast- ing of copper ores, wherein, after roasting, the oxide of iron in the lump is found to be altered until it sur- rounds a globule of rich sulphide of copper. However satisfactory the experiment was, as explaining the action of roasting on pyrites, it is not one which can be lightly undertaken, for after being tried four or five times with excellent results, it was found that some portion of the process so affected the objective of the microscope as to destroy the definition and render valueless a lens worth some three or four pounds. B 3. Base minerals associated with the gold invariably coat the surfaces of gold particles to a large per- centage of the total quantity contained in the ore, and also give rise to complicated chemical reactions ; the effect of either or both actions is to prevent amalgamation and allow the gold to be carried into tailings or down stream. Losses. 61 The losses detailed under head A 4 will in many instances be identical when examining this case. In the first case they may arise from artificial causes, that is to say, causes apart from the nature of the ore ; here they may arise from similar sources, added to detrimental effects produced by constituents of the ore itself. In Ure's Dictionary, Supplement, the following is recorded as the result of Mr. J. Cosmo Newbery's investigations in Australia : . . . . : It must be remembered, however, that in some of our quartz veins, native silver, native copper, native antimony, and native bismuth occur, and these may so reduce the value of the amalgam, or interfere with amalgamation, so as to lead to the inference that there has been neglect or fraudulent attempt to cause loss to the quartz miner. Gold containing arsenic is more difficult to amalgamate than pure gold. If much arsenic is present the amalgam is powdery and black, and floats on the surface of the mercury ; the black colour is due to the separation of the arsenic. This black powdery metallic arsenic does not unite at ordinary temperatures with mercury to form an amalgam, but it mixes with it, coating each globule with the black powder, thus pre- venting their uniting with each other, or, in other words, causing the mercury to flour. Sodium amalgam aids the union of mercury floured by metallic arsenic, but if arsenious acid (common white arsenic) is present it reduces it to the state of metallic arsenic. Arsenical pyrites act seemingly in the same way as metallic arsenic with mercury ; when ground with it a large amount of black floured mercury is produced. If the pyrite is partially decomposed, this action is more energetic than with the original mineral. I could detect no actual combination with the mercury. The black coating was examined under a microscope, but only seemed to be a mixture of pyrites, grains, and globules of mercury, both very finely divided. When the mercury, covered thinly with this black coating, is warmed, the coating is ab- sorbed into the mass and is liberated again as the mercury cools. Sulphide of antimony is perhaps the worst mineral with which the quartz crusher has to deal. It divides the mercury into a black flour even more quickly than arsenical pyrites, and if this flour is triturated with the intention of bringing the globules of mercury together, a chemical combination takes place. The mass gradually changes colour, passing from the original blue-black, or dark-grey, to a, pure black, and then through brown to a brown-red. Upon exami- 62 Losses. nation I found that the remaining mercury contained antimony, and that the brown-red non-metallic portion, consisted of mixture of undecomposed sulphide of antimony and sulphide of mercury. Sodium amalgam was found to be worse than useless in bringing the globules of mercury, floured by sulphide of antimony, together. When only containing a small percentage of sodium it had no action, and when made stronger (sufficient sodium to cause only a slight evolution of hydrogen when the mercury was placed in water) it decomposed the sulj. ide of antimony, forming sulphide of sodium, an amalgam of antimony and mercury and sulphuretted hydrogen. Sodium amalgam also reduces the metal from an oxide of antimony. Bismuth the sulphide causes the quicksilver to separate into flour, and gives rise to loss in the same way as the other sulphides. Lead. This metal has a highly detrimental influence in the process, of amalgamation, and is often supposed to be used for fraudulent pur- poses, as a small quantity added to mercury will cause a loss of gold amalgam and mercury owing to the lead amalgam rising to the surface of the mercury as a frothy scum and carrying with it any gold amalgam that may be present, and by forming a coating over the mercury prevents, its taking up any gold that may pass over its surface. The lead amalgam when thus brought to the surface is easily broken up and carried away in a fine state of division by the stream of water passing over it. The whole of the lead amalgam does not rise to the surface at once, and cannot be completely removed from mercury by simple skimming, but the more the mercury holding it is agitated the quicker it rises. The only way to completely remove lead from mercury is by careful dis- tillation. B 4. The partial decomposition of base minerals in refractory ores produce acidulated water, and its tram of attendant evils which act deleteriously in amalgamation, causing granulation of the mercury (sickening or flouring), which prevents the particles from re-uniting, leaving them in a condition to be readily carried by water ; gold, amalgam, and mercury are then in the best possible condition to be carried off by the water into the tailings or down the stream. Losses. 63 The reason of the partial decomposition of sulphides, &c., contained in ores has been dealt with under head A 4, and the production of acidulated water, and the effect produced explained. When dealing with " refractory " ores, all the ill effects set forth under the previous head are likely to be felt, but those which are caused by the nature of the ore are certain to be in an intensified fojip. With what are known as " free milling " ores, the ill-conditions arising from decomposing mineral con- stituents may frequently be absent. Yet in the case of " refractory " ores they are invariably present to a more or less ruinous degree. To enter into the losses under this head would be to reiterate the greater part of what has been written under A 4. B 5. The mechanical effect of heavy mineral particles in the ore, falling through the stream of water, pre- vent contact between the amalgamating surfaces, and eventually cut off and clean the amalgam and mercury from the plates, causing loss of gold amalgam and mercury. As already mentioned under head A 6, minerals of the nature of scorodite, heavy-spar, &c. &c., are some- times present in auriferous ores ; where so occurring, they, most generally, greatly exceed in quantity the metallic contents. The gravity of such minerals exceed- ing considerably those of the silicious and argillaceous portions of the ore, they fall through a stream of water strong enough to carry off crushed rock, earth and refuse, therefore they speedily form a moving layer which covers the plates and prevents contact between the gold and mercury ; their continued action cut the amalgam and mercury from the plates, and these are 64 Losses. carried away by the water, together with the fine gold. In certain highly silicious ores, or where by calcination the gangue has been rendered clean and sharp, a like effect in stripping the plates is produced to that caused by heavy mineral contents. The effect of adding additional water in endeavouring to remedy the defect frequently results in refuse, rock, mineral, metal, and all else being carried away. C. LOSSES OF MERCURY. Continuous stamping, agitation, or grinding causes mercury to form into minute globules; these have the property of collecting Jine films of matter and air particles on their surface, which reduce their relative weights, prevents their reunition, and they are thus in a condition to be readily carried off by water into tailings or down stream. The effect of sulphur, arsenic, antimony, zinc, grease, organic impurities in water, &c., in rendering mercury impure and destroying its property of coalition have, together with other causes of loss, been dealt with under heads A 5, 6, and B 3, 4, 5, when referring to the loss of amalgam. Losing amalgam results in a double loss, that of gold and mercury ; yet much of the latter is frequently carried away before it has taken up any gold ; the losses, however, are so closely allied that it is almost impossible to draw a dividing line be- tween them. If mercury is brought into contact with any finely ground material its surfaces become immediately coated. If at the same time a grinding or rubbing action is carried on, the metal rapidly loses all its former appear- ance and assumes that of the fine material with which it Losses. 65 is mixed. In such a case retorting is about the only method of bringing it back to its original condition. In some cases it cannot be returned, because the action in the retort also affects the material coating its globules or particles, and results in forming a chemical compound. The druggists' stuff, Ryd: ~& Creta, commonly known as "grey powder/' is simply the result of the grinding together of chalk and mercury ; mercurial ointment, its admixture with a lard. The slimes produced by crushing machines, run with water, frequently become almost as greasy as lard, and the action of crushing and pulverising machines, is invariably, in a greater or less degree, that of the pestle and mortar used by the chemist to make both " grey powder " and mercurial ointment. When these properties are known it ceases to be a matter of wonder why such difficulties are experienced in preventing loss of the metal. Every miner knows when amalgamating and washing a prospect how hard it is to get together the finely divided grey-coloured quick- silver in the bottom of a pan. The money value of the mercury lost is not great, but it is the consequent loss of the gold following that makes the consideration of its properties most essential. 66 Remedies, CHAPTER V. REMEDIES. IT is but citing a truism to assert, that any method for whatsoever purpose applied by man, which has in it a feature working in disregard of some natural law, must prove a greater or less failure, just to the extent that it contravenes the particular law involved. In the applica- tion of the methods described for the extraction of gold from surroundings, failure has followed and still follows in like proportion. During the early part of the present century several notable teachers of the science of metal- lurgy sought for and advocated other methods of treating complex gold bearing ores. About forty years ago the question again received a great stimulus, then for the first time it was proposed for their treatment to follow as closely as possible a course similar to that daily carried on by natural forces, as already de- cribed on pages 8-11. Very little of the researches of the past generation are generally known by the present ; in fact, as it will appear, even those who are supposed to have this knowledge possess little or no information on the subject ; this is the only inference which can be drawn from the records of the solvent processes patented during the past forty years. From forty-five years back to the present, the teachers, workers, and patentees appear to havp followed each other in the order set out below : 1845, Eisner, L., Chemist, Berlin. 1843, Bagration, Prince Pierre, St. Petersburg. Remedies 67 1848, Percy, Dr. John, F.R.S., London. 1848, Plattner, Carl Frederick, Assay Master, Royal Freiberg Smelt- ing Works. 1848, Coster, Apothecary, Patschkau.* 1848, Dufios, Dr., Professor of Chemistry, Breslau. 1849, Lange, Herr, Master Smelter, Reichenstein. 1849, Georgi, Manager of Works, Reichenstein. 1849, Richter, Professor of Chemistry, Leipzig. 1851, Guettler, Exhibitor, Exhibition, 1851, London. 1852, Spicker, Charles, Patentee, U.S.A., No. 8729. 1857, Primard, Edouard, of Paris, Patentee, Great Britain, No. 1931. 1858, Deetken, G. F., Nevada, Cal., Introduced, U.S.A. (see Kus- tell's Chlorination). 1859, Henderson, Wm., Patentee, Great Britain, No. 883. 1859. Toussaintand Laiiglois, of Paris, Patentees, Great Britain, No.. 956. 1862, Cobley and Wright, Patentees, Great Britain, No. 1005. 1863, Deetken, G. F., Nevada, Cal., Patentee, U.S.A., No. 37,278. 1864, De Lacy, A. C. L., Melbourne, Patentee, Victoria, No. fjf. 1868, Calvert, F. Crace, F.R.S., Bath, British Association Reports. 1871, Phillips, J. S., "Metallurgist's Companion," SanJFrancisco. 1874, Dahne, J. F. W., Swansea, Patentee, U.S.A., No. 159,647. 1875, Cobley, T. H., Glasgow, Patentee, U.S.A., No. 174,118. 1877, Mears, Dr. J. J. H., Philadelphia, Patentee, U.S.A., No.. 195,381. 1879, Mears, Dr. J. J. H., Philadelphia, Patentee, U.S.A., Re-issue,. No. 8859. 1880, Mears, Dr. J. J. H., Philadelphia, Patentee, U.S.A., Re-issue,. No. 9203. 1880, Schaeffer, C. A., Patentee, U.S.A., No. 267,723. 1880, Mears, Dr. J. J. H., Philadelphia, Patentee, U.S.A., L No. 269,441. 1881, De Figaniere, of Philadelphia, Patentee, U.S.A., No. 267,842. 1882, Evans, N. F., of Philadelphia, Patentee, Great Britain, No. 1063, 1884, Munktell, Henrik, of Sweden, Patentee, Great ^Britain, No. 16,135. 1886, Hargreaves and others, Lancashire, Patentees, Great Britain,. No. 5681. 1886, McArthur and others, Glasgow, Patentees, Great Britain, No. 11,817. * These records cannot be found. - 68 Remedies. 1886, Hannay, J. B., Dumbarton, Patentees, Great Britain, -No. 14,061. 1887, Newbery and Vautin, of Melbourne, Patentee, Great Britain, No. 4609. 1887, McArthur and others, of Glasgow, Patentee, Great Britain, No. 14,174. 1887, Vautin, C. T. J., London, Patentee, Great Britain, No. 15,574. 1887, Pollok, J. H., Glasgow, Patentee, Great Britain, No. 17,495. 1888, Crookes, Wm., London, Patentee, Great Britain, No. 7867. The records of the foregoing, as will be seen, are almost entirely confined to solvent processes ; were the list allowed to embrace others it would become inter- minable, because the records of smelting, electrolytic, and mechanical methods far exceed in number and ramifica- tions those of the solvent processes. The work done by, or the proposals of each investigator, worker, or patentee will be briefly summarised, following in the order of their dates. BAGRATION, 1843. In 1843, Prince Pierre Bagration, working in St. Petersburg, appears to have been the first to have used cyanide of potassium in a process for dissolving gold.^ He refers to the older methods of Elkinton (London), who used a double cyanide of potassium and iron as a dissolving medium, and Jacobi, who used ferrous cyanide for the same purpose. ELSNER, 1845. In 1845, L. Eisner, a German chemist, separated gold from arsenic and tin by treating the hot dry material with a current of dry chlorine gas.-f- He * Bullet de 1'Acad. imp. des sciences, St. Petersburg, 1843, vol. ii. page 146. f Journal fur prakt Chem., vol. xxxv., pp. 310-12, 1845. Remedies. 69 refers tc Rosa, of Berlin, who in 1830,^ advocated this method for the separation of sulphur, arsenic, tellurium, &c., from gold and other metals. The method had previously been advocated by chemists in the early part of the present century. Eisner remarks that tin and arsenic volatilize as chlorides but that gold and platinum do not, and therefore remain when other metals are carried off. PERCY, 1848. Tn the year 1848f Dr. John Percy, F.R.S., of London, at the Swansea meeting of the British Association held in the month of August, read a paper on the extraction of silver from ores by chlorine, also embodying some important suggestions as to the value of chlorine as a means of extracting gold; in the experiments detailed, both gold and silver were extracted from the ore treated by means of chlorine. The paper details a number of highly interesting experiments. J * Handbuch der analytischen. Chemie, 1830, Griffin's English trans- lation of same, 1831. f As these experiments were made public in the same year as other important researches on the subject, the author, in endeavouring to place the records in their proper order, wrote to Dr. Percy and re- ceived the following reply : Dear Sir, I duly received your letter of the 17th inst I can with absolute certainty say that my experiments on chlorine were carried out quite independently of any suggestions made at the time by the German chemists. Until I read your letter I was not aware of the experiments made, as you say, by several German chemists in 1848-9. ... Yours very truly, November 21st, 1888. John Percy. The author was subsequently permitted, by the courtesy of Dr. Percy, to search his old chemical journals, and a record of the carrying out of the experiments, forming the paper read at the 1848 meeting of the British Association, appear between the dates 3rd and 13th November, 1846. J "Philosophical Magazine," 1853, vol. xxxvi., pages 1-8. 70 Remedies. In experimenting on the extraction of silver with chlorine, the ore dealt with was an " auriferous silver ore, which contained a large proportion of blende, with galena, iron pyrites, and copper pyrites in small quantity; the non-metallic part chiefly consisting of silica. The silver was present as sulphuret." Dr. Percy roasted this ore in every case. In one of the experiments he powdered the ore finely, and put 1000 grains in a glass bottle with water, and passed chlorine gas into it for one hour, closed tightly, and shook it up occasion- ally during four days, then filtered and reduced the solution considerably by evaporation, and added hypo- sulphite of soda. He then treated the residual ore with hyposulphite of soda, filtered and washed, and mixed the "filtrate with the previous solution; he added hydrochloric acid and digested, and afterwards got a red-brown precipitate, this he cupelled and obtained a button of metal, and subsequently parted the gold from the silver by nitric acid. He remarked that he thought with proper appliances it would be a good process for workings on a large scale, then finally summarised as follows : I would especially direct attention to chloride of lime and chlorine as agents for the conversion of the silver into chlorides, and to hypo- sulphite of lime, which may be readily obtained as a cheap substitute for hyposulphite of soda to dissolve the chloride. The silver it is obvious might be precipitated either as a metal or sulphuret. Since many of the South American silver ores contain gold, it is desirable that the silver and gold should be extracted by one process ; and to this end chlorine or chloride of lime seems to be indicated by the preceding experiments. PLATTNER, 1848. It is not an easy matter to define precisely the part taken by Carl Fredrich Plattner in devising the process of chlori nation which has for so many years borne his name, or the amount of credit due to him for the dis- Remedies. 71 covery. It would seem that he carried out some experi- ments, to which he attached little importance, so little indeed that he did not publish them or make them known, and had it not been that Mr. Websky (a student at the Freiberg Mining Academy) communicated the results to the authorities, the matter might have, as far as Plattner was concerned, ended there; but, as it turned out, these particular experiments led to detailed investi- gations by other chemists, and that to them are due the credit of further practical experiments from which the subsequent devising of a process resulted. Plattner's name is placed in this order because the German authors writing about this date, mention that he had made certain investigations, and as a result they were carrying out experiments as to the proper method of applying chlorine for the purpose of extracting gold from ores. Professor Plattner was a metallurgist of great repute ; his works on the blowpipe and general metallurgical subjects are to-day standard works of reference ; he held the official position of Assay Master at the Royal Freiberg Smelting Works. His " Die Probirkunst mit dem Lothrohre," Leipzig, 1835, contains no reference to chlorination, although for testing poor ores and mattes for gold, a process -of roasting and subse- quent treatment with hydrochloric acid is mentioned, pages 291-3. His next work did not appear until 1853, his reference to chlorination in this will be given in full, later on. In his " Die Metallurgischen Rostprozesse," Freiberg, 1856, when writing on the practical treatment of ores by chlorination on a large scale, he refers on page 274 to the "very complete researches on the subject, undertaken by master smelter Lange" (Karsten's Archiv, vol. 24, p. 396 and B.u.h., 1852, p. 169), these also 72 Remedies. will be detailed on pages 77 to 83 in their proper order. In 1848, Dr. Duflos, of Breslau, made a series of experiments which are detailed in " Die schles. Gesell. Uebersicht," 1848, pages 27-9 ; int his paper he casually referred to previous experiments which had been carried out at Freiberg, and later on in the paper acknowledges the previous experiments of Coster, and other experi- ments at Tarnowitz and Friedrichshlitte. In the " Journal fur praktische Chemie," vol. xlviii., pages 68-70, this paper by Dr. Duflos is reprinted in the form of an editorial, without any reference being made to the original source. Again, in the "Jour, fur prak. Chem.," 1849, vol. li., page 151, Theo. Bichter wrote as follows : The use of chlorine water for the extraction of gold from poor auriferous ores was first suggested in 1848 by Plattner, of Freiberg, after he had made experiments on a small scale and had sufficiently satisfied himself of the usefulness and adaptability of the method. Plattner made his experiments with residuals of the roasting process containing arsenic ; these were obtained from Reichenstein, in Silesia, by the kindness of Mr. Websky, who was then studying at the Freiberg Mining Academy. . . . As these residues contain only a very small quantity of gold (probably only from % to ^ loth per cwt.)* they cannot be economically worked by any smelting process. These residues had accumulated in large quantities, and it was of great importance to extract the gold from them by a rapid and cheap method. After Plattner had satisfied himself by qualitative analysis that these residues consisted chiefly of a mixture of oxide of iron, peroxide of iron, and basic arsenical iron oxide, he treated the same without any other preparation in a large closed retort with fresh chlorine water, and he succeeded in extracting in his first experiment T ^- loth per cwt., and in his second experiment improved this to T \ loth. These experiments are the same which are casually referred to on page 68 of vol. xlviii. of this journal, as having been conducted in Freiberg for extracting gold by this process. It was these experiments, the successful results of which Mr. Websky mentioned to the author at the time, which were the cause of other experiments being * 3000 loth = 1 cwt.. Remedies. 7& carried out on a larger scale both in Reichenstein and other places showing the practical utility of Mr. Plattner's method. The foregoing is the only reference to Plattner's- original experiments which can be found, and even this suggested reference is very ambiguous. It is possible that in some old German literature, or in some unpublished paper, Plattner wrote of his discovery at the time, but an exhaustive search in nearly all the public and scientific libraries in London has failed to reveal it, and application a few weeks ago through Mr. Alfred Borns, of Habelschwendt, in Silesia y to the authorities of the Mining Institute of Tarnowitz r has produced no more satisfactory result. German authors do not appear to have been more successful, for in Karsten, Kerl, and others (in all of which most elaborate references are given), whenever Plattner is referred to for chlori- nation, it is simply by name alone, or the later reference of " Probirkunst, 1853." It would in a measure destroy the sequence of the story to give this reference here ; it will appear on pages 89-93 in the order of its date. DUFLOS, 1848. Dr. Duflos, of Breslau, a chemist of note, who wrote largely from the years 1828 to 1855, carried out a series of experiments, under the auspices of the Royal Ober- Prasidum, for the purpose of seeing whether practical metallurgical operations for gold could be carried out on the Reichenstein arsenical residues. A free digest of the paper read by Dr. Duflos on the 26th December, 1848, at a meeting of " Die schles. Gesell. fur vaterlandische cultur," detailing his experiments, is as follows : In the first place, to satisfy himself that it was feasible experimentally, he put 1 5 Ib. residues and 15 Ib. of water 74 Remedies. into a glass bottle, leaving one quarter of it empty, this lie filled with chlorine gas, then tightly closed the bottle with a glass stopper and rolled it up and down a table for two hours. He then removed the liquor by a suction tube and again twice treated the residues in the bottle in the same manner. The solid matter was put into three conical funnels placed over glass cylinders, but first of all the stems were filled with a filter of coarse and fine sand. The stuff in the funnels was then twice washed with chlorine water, the combined liquors in the experi- ment were evaporated to ^ Ib. in weight, then saturated with chlorine gas and filtered, the free chlorine was driven off by warming, and the solution mixed with a solution of arsenious acid. After twenty- four hours the clear liquid was poured off from the deposited gold, which was washed with hot distilled water, and dissolved in aqua-regia ; this was poured into a porcelain dish, evaporated to dryness, heated to redness, and the gold weighed. To be sure that his deductions were correct he conducted this whole experiment a second time and got a slightly better result. As a third experiment he put 15 Ib. of residues into three glass funnels, then poured chlorine water over the residue in the first funnel and covered it with a glass plate, when the liquor began to drip through, the funnel was refilled with chlorine water, and the quantity which had dripped through was re-saturated with chlorine and poured into the second funnel. When it had dripped through this it was again saturated with chlorine and poured into the third funnel, the second funnel was refilled from the first, and so on, until the operation had been performed three times on each funnel. The total liquor then amounted to 16 Ib., it was put into an open Remedies. 75 dish, and when the chlorine odour had disappeared it was acidified with hydrochloric acid and treated with arsenious acid for precipitation. After standing for two days no gold was left in the liquor, which was then evaporated to -^ Ib. in weight, the precipitate filtered out, washed and dissolved in chlorine w^ater and poured into an open take up the moisture. This charge part as well as the moistened, as described before, must be subjected to Sifting. This operation takes but a short time and is necessary for two reasons. One is the separation of lumps and crusts formed during; the roasting, and of other impurities which might drop in accidentally,. all amounting to 2 or 3 per cent. The other reason is the required loose condition of the ore in the vat, which is best obtained by passing; it through a sieve. For this reason the sifting must be performed directly into the vat. The sieve is 12 in. to 14 in. by 25 in. in the clear r the sides 5 in. high. The sieve is sufficiently fine if there are seven to- eight meshes to the running inch. A chlorination vat, into which the ore is sifted by pushing the sieve- to and fro, either on two scantlings laid over the rim of the tub, or suspended on four ropes. In Fig. 4 is represented a vertical cross- section of a circular vat, 7 ft. in diameter, capable of holding 3 tons of roasted sulphurets. Above the bottom b is an empty space over the whole bottom 1 in. high formed by the false bottom a, the boards of which are laid together, leaving about J in. space between them. Besides this there are J in. holes bored in it from 10 in. to 12 in. apart. The boards are supported by short pieces c, leaving sufficient space for Remedies. 10T the passage of the chlorine. Over the false bottom is spread first a. layer of clear quartz from 1 J in. to 2 in. in thickness. In default of quartz another kind of rock will answer the purpose provided there is no lime or talc (sic) in it, which would absorb a considerable amount of the chlorine ; and if notice is not taken of the character of the rock the greater consumption of chlorine might be supposed to be the con- sequence of defective roasting. Over the coarse layer smaller pieces are laid, and so on, decreasing in size till a layer of sand covers the whole, forming thus a filter of from 4 in. to 5 in. in thickness. This filter remains always in the vat; the shovelling out of the residue therefore must be done carefully on approaching the filter bottom. There are two holes communicating with the space below the false bottom. One is for the reception of the lead pipe d, by which the chlorine is introduced ; the other is provided with a leaden cock c, for discharge of the lixivium. This side of the vat stands J in. lower. The wooden vat would absorb a great quantity of the gold in solution! if the inside were not coated with some material which prevents^ the soaking in of the fluid. Mr. Deetken uses one part pitch melted and one part of tar. This is a cheap and quite suitable mixture, and is applied by means of a brush when hot. It is a matter of course also that the boards of the false bottom should be coated carefully on all sides, as well as the whole of the inside. There are also vats or tubs 5 ft. in diameter 3 ft. high, holding two tons of roasted sulphurets. Three or more of them are arranged in one row, as shown by Fig. 5. They are conveniently managed, and preferred where small charges of custom ore are to be treated. Deetken introduced successfully a large vat of 10 ft. diameter 2 ft. high, constructed exactly like Fig. 1. This vat is capable of holding from 6 to 7 tons of roasted sulphurets. The usual charge is 6 tons. 108 Remedies. There is doubtless more economy in treating 6 tons in one vessel than in two or three of a smaller size ; there is less waste of material and some saving of labour with the larger size. Chlorination vats with a greater diameter are preferable to higher tubs of the same capacity ; for the reason that a low column of sulphurets assumes a less dense condition, and also because of the greater cukic contents of the free space above the sulphurets which is filled with the chlorine, so that an accidentally greater consump- tion of the gas can be replaced. The cover g, Fig. 4, must fit as well as possible in the step of the 6. vat side, but not too tight ; the planks, however, have to be fitted together tightly with tongue and groove. For the purpose of lifting there are generally three or four chains fastened to the cover. Ropes are of no use as they are destroyed in a short time by the gases. The moistened ore, as before said, is sifted directly into the vat over the filter. In order to avoid a condensed charge, it is necessary to move the sieve from one place to another till the whole charge is intro- duced; the surface is then made even, and the charge is ready for chlorinatiori. The chlorine gas is produced in a leaden vessel, as shown in Figs. 6 and 7 ; the first is a vertical cross-section, the second a top view Remedies. 109 with the cover on. The circular tub a has an outer ring c six inches deep, for the reception of the ring-shaped side of the cover b. A similar small ring d l is on the top of the cover which receives the collar e, fastened to the leaden stirrer /. There is also a short leaden pipe g, bent in the shape of the letter S, through which the sulphuric acid is introduced, the outer end forming a funnel for this purpose. Another lead pipe d conveys the chlorine to the vat. The cover is taken off, and for a charge of three tons of roasted sulphurets is introduced the following : 30 Ib. of manganese (peroxide) pulverised, 30 Ib. to 40 Ib. of common salt, according to quality, 75 Ib. of sulphuric acid of 66 deg., and 45 Ib. of water. The water, salt, and manganese, are introduced first, and the generator covered.* The two rings c and d l are filled with water, and thereby the con- tents of the generator shut up air-tight, with the exception of the two lead pipes g and d of the cover. The gas generator stands over a small furnace, as represented by b, Fig. 5. The sulphuric acid is now introduced through the pipe g, Fig. 6, but not all at once. Three bottles are generally sufficient to create so much heat that the develop- ment of the gas takes place in sufficient quantity* No fire is yet made under the generator. The chlorine is not conveyed directly to the chlorination vats, but through a purifying apparatus, as represented in Fig. 8. An ordinary wash-basin, or some other similar vessel A, receives two lead pipes (fin.); one of them, d, conveys the chlorine from the generator, and is bent a little upwards ; the other is bent in the same way but stands higher. Both ends are covered with a bottle, the bottom of which is cut off. There is sufficient clean water in the dish to stand J in. or f in. above the mouth of the pipe c?, so that all the gas which enters the space in the bottom is forced through the water, which takes up the muriatic acid. The chlorine passes then through the pipe d u , which is as long as may be required by the distance of the vat, enters the space below the false bottom, and gradually permeates the ore. The water through which the gas passes absorbs, if cold, about two and a half volumes of the chlorine, and is then saturated, but is still good for the purpose of taking^ up muriatic acid. The warmer the water is, the less chlorine is absorbed. It is, therefore, wrong to introduce a continual stream of cold water into the * The leaden gas generator costs about 120 dols. The bottom is made of 1 6 Ib. and the sides and cover of 8 Ib. sheet lead. 110 Remedies. wash-basin A, as is done in some places, as a good deal of the chlorine is lost thereby. The water in the basin may be renewed once or twice during the operation with warm water. This apparatus is not only for the absorption of muriatic acid since, if a portion of this should happen to enter the vat, and, forming sul- phuretted hydrogen, precipitate metallic gold, this would be converted again into chloride in presence of abundant chlorine but the apparatus is an indispensable indicator of the gas generator. The bottle 6, Fig. 8, must show greenish gas, and the bubbling from the pipe d must be very lively. If this should not be the case, another bottle of sulphuric acid must be introduced, and the addition continued as often .as the development of the gas becomes weaker. After the last bottle has been used up a moderate fire must be made below the gas generator. The arch 0, Fig. 5, is very flat, and only 2 in. thick in the middle. Care must be taken to have a J in. layer of sand over the arch ; an open crack would cause the melting- of the bottom of the lead vessel. It is also necessary to turn the stirrer f, Fig. 6, now and then carefully to prevent the caking of the ingredients. The vat, after the ore has been sifted in, as before described, is left uncovered. It takes from three to six hours before the gas reaches the top of the charge. The progress can be easily watched by taking samples from underneath the surface. The smell of the chlorine shows how high it has penetrated. When the chlorine odour is perceived within a few inches of the surface of the charge, the cover is laid over the vat, and the edge i, Fig. 4, all round the cover, luted with dough of wheat-flour. If there be any cracks in the cover, they must be carefully pasted so that no chlorine can escape anywhere. The only opening not shut is a hole of 1 in. diameter, k but as soon as the gas commences to escape, that is plugged up with dough. The circular opening I in the cover is only proposed by the author, and explained further on. The chlorine is now permitted to operate on the gold for twelve to eighteen hours (it may be added that, as the sifting requires some time, if the charge amounts to 3 or 6 tons, the gas generator can be put in operation before the vat is entirely filled with ore, because the ascension of the chlorine is also slow). The pipe d n is removed and the hole plugged up. All the apparatus must be examined at intervals to see that there is no loss of gas, or at least whenever such loss should be perceived by the odour. For this purpose ammonia serves. A glass rod dipped into it and carried close around the place where the loss indicated by the smell will immediately give off white fumes when in contact with the chlorine, and show the place where it escapes. To prevent the drying of the dough around the cover, it may Remedies. Ill be covered with strips of wet cloth. For the production of chlorine the following is also used : one part manganese, two parts muriatic acid, one part sulphuric acid, diluted with one part water. Lixiviation. After twelve or if the sulphurets contain coarser gold, after fifteen to eighteen hours the cover is taken off and water introduced. If it should happen that in taking off the cover no gas is found over the ore, it is advisable to shut the vat and to impregnate the ore again with chlorine immediately, as in nine times out of ten the ex- traction of gold will fall short. This, however, does not occur often with proper management. The water should flow in quickly and in such a way as not to strike on one point producing a deep hole in the mass. The cock e is shut, and the waterflow continues until the surface of the charge is covered and no air bubbles appear. The water is then stopped and the cock e opened. A small stream of water into the vat must replace as much as flows through e, so that the surface of the ore is always covered. The respiration of the chlorine is injurious, and it is therefore advis- able to avoid the inhaling of the gas as much as possible by leaving the room until the gas disappears. The best way would be to have an ar- rangement by which the gas is carried out of the building ; for instance, to put a movable wooden pipe 6 in. square about the proposed opening I.* In order to prevent the stream of water from making a hole into the ore a perforated wooden distributor fixed to the cover, as shown in the drawing, would answer the purpose. A trough below the cock e receives the solution and conveys it into the precipitating tub e (Fig. 5). The trough must be lined with sheet lead, avoiding sharp corners ; or it must be at least well coated with tar ,and pitch in default of sheet lead. Great care must be taken to pre- vent the waste of the solution. Not a drop of it ought to be seen outside of the trough. The precipitating vat e, Fig. 5, is a wooden tub like the chlorination vat, Fig. 4, but without a false bottom. The staves must fit together perfectly. One 4 ft. in diameter and 3 ft. high is sufficient to receive the solution of 3 tons of ore. Deetken's 10-ft. vat containing 6 tons of sulphurets requires two precipitating vats, one is 5 ft., the other 6 ft. in diameter, each 2 ft. high. The vats ought to be lined with sheet lead, and a more proper shape would be a rectangular box with a half- * More convenient would be a leaden pipe through the side of the rat near the top, through which the gas is forced, by the entering water, out of the building. In this case the water would have to be conveyed by -an india-rubber hose through the opening I of the same size with the Jiose. 112 Remedies. round, somewhat inclined, sheet lead bottom, which permits an easier and better cleaning. In default of a lead lining the vats must be coated! with a mixture of pitch and tar, otherwise the wood absorbs some of the gold solution. A better and smoother coating is obtained by the use of the so-called " asphaltum cement," which should be applied twice before it is ready for use, as the cement is too liquid for a single coating. A very smooth surface of the vat is important, else it is difficult to gather all the finely precipitated gold. From time to time samples are taken in a clean tumbler of white glass from the solution at the end of the trough, and observed in refer- ence to the point whether an addition of a clear solution of sulphate of iron (green vitriol) causes a dark precipitate. If the solution after the- addition of the precipitant should remain perfectly clear, the water supply in the chlorination vat must be stopped and all the liquid con- tents of the vat permitted to flow into the precipitating vat. Precipitation. The precipitant for the gold is a solution of sul- phate of iron. It is known also under the name of " copperas " or green vitriol, and forms light green crystals. Dissolved in water (in a barrel 20 in. or 22 in. in diameter and about 3 ft. high) it generally makes a- muddy solution and gives a light sediment which must not be disturbed in drawing off the clear solution from above it. For this purpose a leaded syphon will answer. It is, however, better economy to prepare the precipitant fresh in the chlorination works. In a barrel or tub of about 10 cubic feet content, 50 Ib. to 60 Ib. of pieces of old wrought iron are introduced, then five or six buckets of water and 20 Ib. to 30 Ib. of sulphuric acid. This is prepared two or three days before the solution is wanted. One or two buckets of this iron solution must be introduced into the precipitating vat before the gold solution is allowed to flow in, so that the precipitation may begin immediately. After this as much of the precipitant is added as is required, which can be ascer- tained by taking a sample out of the precipitating vat, filtering it through filtering paper, and mixing it with the precipitant. If the mixture should darken a little after a time some more of the iron solution must be introduced into the precipitating vat. The precipitated gold requires- some time before it is all deposited on the bottom. The fluid must appear perfectly clear before the water can be drawn off. Generally the mixture stands undisturbed over night. The upper plug g (Fig. 5} is removed and the clear liquid conveyed into another vessel f, of suffi- cient capacity, till it is nearly all run out of the precipitating tub- through all the plug-holes. The discharge must be performed carefully so that the flow appears always clear. It is better if several chlorina- tions have been performed before the gold is taken out, as there is a, Remedies. 113 less percentage of loss by wastage with a large quantity of gold. This is dipped out carefully by means of a dipper or scoop into a clean porcelain dish or enamelled vessel, and the rest washed out through the lowest cock. It is well to apply a jet of water over the sides and bottom in order to wash off all precipitated gold. The gold obtained is then introduced into a filter of filtering paper, and subsequently dried in an iron or porcelain vessel in a warm place or over a fire. For the purpose of melting the black lead crucibles are less suitable than "Hessian" or clay crucibles; from the latter a purer gold is obtained. A little salt, some borax, and saltpetre (nitrate of potash) are added as fluxes. COST OP THE CHLORINATION PROCESS PER TON OP ORE. If the ore is roasted in a long or double furnace a ton of well roasted sulphurets can be drawn out every eight hours, that is, 3 tons in twenty- four hours. The working expenses of twenty-four hours may be given .as follow: $ Superintendence ... ... ... ... ... 6.00 Four roasters at $3.50 H.OO Three cords of wood at |4 12.00 Thirty pounds manganese at 6^ c. ... ... 1-87^ Forty pounds salt at | c .. .30 Seventy-five pounds sulphuric acid at 2J c. ... 1.87J One man at the vats, two days at $3.50 ... ... 7.00 Sulphate of iron ... ... ... ... ... 60 Total cost of 3 tons $43. 65 Or $14.55 per ton of sulphurets. That the foregoing process is in general use in the United States, and other parts of North and South America, may be judged by the following plan and excerpt from the catalogue of 1885 of Messrs. Fraser and Chalmers, Chicago, &c., who are probably the most enterprising manufacturers of metallurgical machinery in the world, and who, had there been anything better de- vised, would assuredly have endeavoured to introduce it. CHLORINATION MILL. This mill and process as used in connection with a gold mill for 114 Remedies. treating the concentrates from the Frue vanners is clearly illustrated in an article recently published describing the Providence Mill, Grass Valley District, California,* which we reproduce : " The ore treated is quartz, carrying free gold, pyrites, galena, chal- copyrite, arsenopyrite, and zinc blende. It is first crushed in rock breakers and then stamped fine enough to pass through a forty-mesh sieve. Then it passes as a slime over silver-plated copper amalgamat- ing plates to Frue concentrators. The free gold is caught in the stamp Fig. 3. batteries and on the plates, the sulphurets are collected by the concen- trators. The latter are dried and then roasted, chlorinated and leached. The roasting is done in a three story reverberatory furnace. About 1 per cent, of salt is added near the close of the operation. All the sulphur, arsenic, and antimony are expelled and the iron and other base metals oxidised. The gold is left in a free metallic state, the silver being partly concentrated into a chloride by the salt. " The roasted ore is then transferred to chlorinating tubs, holding from 2 to 3 tons each. The covers are put on and the joint caulked with rags and luted with dough to make it gas-tight. The tubs have false bottoms, full of holes and covered with sacking. Chlorine gas, * Near where Deetken worked twenty-seven years previously. Remedies. 115 made from salt, black oxide of manganese, and sulphuric acid, is then introduced below the false bottom and allowed to permeate the ore. Two or three days are required for their permeation. The gold and silver are thus concentrated into chlorides. The chloride of gold is leached out by water added at the top and drawn off at the bottom and run into precipitating tanks. The gold is precipitated in a fine metallic state by the addition of sulphate of iron. The water is then run off, the gold collected and dried, melted in graphite crucibles and cast in bars. " The silver chloride remaining in the ore is dissolved out by a solution of hyposulphite of calcium. The solution is run into other tanks and the silver precipitated as a sulphide by adding calcium polysulphide. The sulphide of silver is dried, roasted, and then melted and cast into bars. The cost of milling and treating the sulphurets is 1.37 dols. per ton of ore." One of the main faults of this process is the great length of time necessary for the chlorine gas to permeate the ore and dissolve the gold, also the time occupied in the filtration and subsequent separation of the metal from liquid and its surroundings. Taking as a basis the state- ments put forward by Messrs. Fraser and Chalmers, a mine turning out 100 tons of ore daily would require to run without stoppages, at least 100 vats, this is a triple vat capacity to that required for one day's output, and creates a very considerable item both in cost, and shed capacity, to which should be added at least another hundred vats to take the leachings from the chlorinated ore, prior to the precipitation of the gold ; so, for a mine of the specified output, some 200 vats would be required ; yet, with a mine turning out ore, from which the aggre- gate quantity requiring chlorination amounts to only a few tons per week, this is still perhaps the most econo- mical process. HENDERSON, 1859. Mr. Wm. Henderson's patent, No. 883, is dated April 8th, 1859, and refers to the following : 116 Remedies. Improvements in treating certain ores, and in obtaining products therefrom, to be as follows : These improvements relate, first, to the treatment of zinc ores, or other ores containing zinc ; secondly, to the treatment of ores of anti- mony that contain lead and other metals ; thirdly, to the treatment of copper ores ; fourthly, to the treatment of ores or products containing cobalt ; fifthly, to the treatment of gold and silver ores and auriferous quartz ; and, lastly, to the dressing of lead and other ores. From this specification extracts are made which refer to the principal points of his method of treating gold, and silver ores. In his procedure he follows previous chlori- nators to this point : When the ores are very soft and friable it is necessary to work them in round agitators (1). I prefer, however, to work these ores in vats with false bottoms, when at all practicable. A vat having been filled with the powdered ore, I cover the whole surface of the ore with muriatic acid, of about 15 deg. Twaddle's hydrometer, and allow it to penetrate through the body of ore. The acid must not contain any free chlorine. When the whole of the ore has been wetted with muriatic acid it is allowed to rest for a few hours. The liquor is then washed out with water until perfectly tasteless. By this means I separate all oxides and earths soluble in muriatic acid ; if these are of any value they may be separated from the solution as previously described (2). The quartz thus prepared is now covered with aqueous solution of chlorine, and the solution of the gold at once takes place. A gentle heat much facilitates the solution. The liquor during the process of solution should be repeatedly pumped to the top of the ore and allowed to penetrate under the false bottom, leaving the top of the ore dry, and as soon as this occurs it must be all pumped to the top again, so as to keep up a constant circulation. If these directions are carefully attended to, the whole of the gold will be dissolved out from even rich quartz in twenty-four hours (3). The chloride of gold is then removed to another vessel, and a sample of the ore tested for gold ; if any remains undissolved, a further quantity of solution of chlorine is added until the ore is exhausted. It is then washed thoroughly clean and the washings added to the original solution. The solution of gold thus obtained is then boiled by a jet of steam to liberate the free chlorine (see Hears subsequently). If this is done in a close vessel the chlorine gas may be again condensed by passing it through cold water. When the boiling solution smells no longer of chlorine the gold is then precipi- tated by protosulphate of iron, oxalic acid, or any other precipitant (4). Remedies. 117 .... In some varieties of gold quartz the gold is only partially dis- solved, sometimes not at all, by aqueous solution of chlorine, nor by chlorine in the gaseous state (5). These ores I treat in the following manner: I treat the ore either before or after the washing with weak muriatic acid ; if the latter I dry it, and then intimately mix it with from 1 to 5 per cent, of good peroxide of manganese (or other oxide capable of liberating chlorine from muriatic acid) in fine powder. I then moisten this mixture with strong muriatic acid of at least 1.125 specific gravity, turning over the heap so as to ensure that every part has been moistened. The heap is then gathered closely together, and allowed to heat of its own accord in a dry place for twenty-four hours. At the end of that time it should be transferred to the vats with false bottoms, and the vats filled (6). Steam of a high pressure (say 60 Ib.) is then slowly introduced under the false bottom, from which it will gradually penetrate upward through the whole mass of ore (see Primard previously}, dissolving the chlorides of gold and manganese, which are drawn off from under the false bottom into another vessel, and the ore may then be entirely exhaused by washing with hot water (7). The gold will be readily obtained from this solution by boiling with protosulphate or protochloride of iron. I prefer the former. A mixture of common salt and oxide of manganese may be mixed with the ore, and then the mixture, moistened with concentrated sulphuric acid, may be substituted for the oxide of manganese and muriatic acid ; but I prefer the latter as simpler and cheaper (8). (l.) This appears to be an ambiguous reference to barrel chlorination. (2.) From an economical point of view such procedure is quite impracticable, and might result in producing arsenuretted hydrogen, a very deadly gas. (3.) Such procedure would be impracticable except with clean quartz, for with ores that produced slimes a rapid clogging would result, and the liquor could not be continually passed through them. (4.) This boiling method can only be regarded in the light of a laboratory experiment ; from the leaching the resultant liquid must be at least equal in quantity to the bulk of ore treated, and the whole solution would have to be boiled in a vessel not acted upon by chlorine. The 118 Remedies. value of the chlorine saved would not pay for boiling and condensation. (5.) It is difficult to arrive at what the patentee here means. (6.) This appears to be the first suggestion for the generation of chlorine within the ore mass in the manner described. Duflos and Lange, in 1848-9, both generated chlorine in the ore when in the chlorinating vessels ; the advantage of generating chlorine in the ore before put- ting it into the vats is not very apparent. The quantity of muriatic acid required precludes the carrying out this method within the limits of economy on a goldfield. (7.) This is an inverted method of Primard's leaching process, as he introduced the steam on the top of the ore. (8.) With perfect mechanical arrrangements these suggestions are good. The remainder of the patent specification deals with the subject of crushing by rolls, which are favoured by Mr. Henderson. Similar views to those expressed by him have been lately put forward as original by several writers on the subject. TOUSSAINT AND LANGLOIS, 1859. For the patent, No. 956, issued to Messrs. Toussaint and Langlois, of Paris, the provisional specification is dated 16th April, and the specification 14th October, 1859, from which the portions referring to chlorination are abstracted : This invention relates to apparatus for the separation of ores of gold, silver, and other minerals. This separation is performed in three different ways by chloruration, the application of a column of water, and by amalgamation. The first apparatus for effecting the chloruration permits of creating a vacuum before the introduction of the reducing agent, which then permeates the ore without resistance, and completely saturates it. The Remedies. 119 metallic chlorides are after the operation treated in the ordinary way. I have represented in the drawing (Fig. 10) a complete apparatus for the treatment of ores of precious metals by means of chlorine, a, wood recep- tacle lined with lead to contain the ores ; b, cover of the receptacle on which it is firmly bolted ; c, masonry supporting the receptacle a ; d, funnel cock of lead placed on the cover 6, which serves for the introduc- tion of the ore into the receptacle a ; e, vacuum gauge ; f, ordinary gauge ; 153, QUEEN VICTORIA STREET, LONDON, E.C, WORTHINGTON PACKED PLUNGER PUMP. MINE PUMP. MINE PUMP. PRESSURE PATTERN. PRESSURE PUMP. WORTHINGTOM PUMPS FOR ALL SERVICES. FEED PUMPS; MINE PUMPS; SINKING PUMPS; &c. &c. CATALOGUES AND PARTICULARS ON APPLICATION; ROBEY & CO., MANUFACTURERS OF MM MACHINERY Of ALL DESCRIPTIONS, INCLUDING With WOOD or STEEL FRAMES. Improved STONE BREAKERS, High-Speed ORE CRUSHING ROLLS, GRINDING and AMALGAMATING PLANTS. ALSO OF tfHE "ROBEY" MINING ENGINE & BOILER With Patent Wrought- Iron Tank Foundations, SPECIALLY ADAPTED FOR EXPORT AND UP-COUNTRY TRANSPORT. MINE PUMPING MACHINERY, PIT HEAD FRAMES, &c. STEAM ENGINES OF ALL DESCRIPTIONS. MAKERS BY SPECIAL LICENSE OF THE NEWBERY-VAUTIN RAPID CHLORINATION PLANT. FOR CATALOGUES AND PARTICULARS APPLY TO- ROBEY # CO., Globe Works, LINCOLN. 390306 UNIVERSITY OF CALIFORNIA LIBRARY ilNES HORIZONTAL SHAFTS, FOB Falls up to 50 feet, AND GIRARD TURBINES VARIABLE WATER SUPPLIES. WITH HORIZONTAL SHAFTS (Running at comparatively slow speeds), FOR FALLS FROM 60 ft. to 600 ft. AND HRIABLEJATEB SUPPLIES, Turbine Governors, Supply Pipes, Gearing-, and all Accessories. Catalogues and Prices on Receipt of Particulars. LONDON AGENTS: CHAS. APPLEBY & CO., 89, Cannon Street, E.G. H X W XI GO GO I H w XI n GO r^ ij s \ H -T Q s W tf 2 L^ 1 CO Q < f VER MEDAl A. SOCIETY, 1883. )LD MEDAL, INTERNATIONAL BITION, 1884. VER MEDAl INTERNATIONAL BITION, 1884. VER MEDAl STITUTE OF SCOTLAN il> MEDAL, INTERNATIONAL BITION, 1885. FJBJB MEDAl INTERNATIONAL BITION, 1885. Order of Mer )E EXHIBITION, FJ5JJ? MEDAl HIGHEST AWARD), ^STITUTE OF CORN 1683, S tf i 4 &Z 3UTTA a : - & ^0 }Z5 M ^ & WERP 1*0 Pn uJ 03 %$ *fc^ I-H ^ 2 ^ IS, W i ^~ rH M O g M 2 & H H "* ft *H ! o 3 ' 3 5 ^ 1 H Q Z < 5 z LU UJ LL LU ^ < CO ^ DC O LU CL O DC UJ Q 2 in I Electrical Chlorination. The first practical demonstration of the ex- traction of gold by means of chlorine, is due to the late Professor Plattner, upon whose dis- covery all subsequent improvements are based. The most noteworthy modifications and im- provements are those of Calvert, Jackson and Ott, Hears, Deeken, Patra, Rceaner, Hauck, Newberry and others of less note. The intro- duction of electricity in the extraction of gold is of more recent date, and the leading names of those who first adopted this method are Pichenor, Ancel and Marie, and Cassel. The latter patent was approved by capable author- ities, but although five years have now passed, Cassel's process has not forged its way to the front. Mr. Th. Ranft, M.E., of Sydney, says the Australian Mining Standard, now introduces an electric-chlorination process, in which he claims to have overcome the vital defects be- fore experienced in electrical chloriuation, viz., the getting rid of the sequent hydrogen and sodium as they are formed by the electric cur- rent when passing through the electrolyte. In all processes where the hydrogen cannot be kept separate from the chlorine gas, the two will combine and form hydrochloric acid, which combination does not solve gold and is in every way most injurious to the process. The in- ventor does not claim or patent any new law, but an apparatus by means of which the laws observed are complied with. The apparatus consists of two cylinders, one within the other. The inner cylinder, made of a porous material, serves four functions, viz., 1st, as a filter, 2d, as the negative pole or cathode; 3d, it acts as a burrette to allow the precipitated gold to es- cape along with the caustic soda, and lastly it allows the formed hydrogen gas to escape at the top. The outer cylinder, which is air tight (except at the places where it is required periodically to discharge) serves three pur* poses; firstly, it forms the positive pole or anode of the battery; next, it acts as a chlorine gas generator and store, and lastly, as the chlorina- ting vessel. The process performed in the apparatus is as follows: The ore to be treated (free of sulphur, arsenic, lead, zinc or bismuth) is mixed in cer- tain proportions with common salt. It is then fed into the outer chamber, where the anode is, and the electric currents enter. Water is then added, which dissolves the salt in the ore, and this combined with the saline liquor, forms the electrolyte. An electric current from a dyna- mo it then led into it by the anode, and pass- ing through the solution into the inner cham- ber or cathode, is discharged back to the dy- namo. The chemical actions produced by the passage of the electricity is to decompose the electrolyte into its elements. Hydrogen and oxygen are the products of water, chlorine and sodium those of salt. Hydrogen, being a posi- tive substance, deposits on the negative pole; oxygen, on the other hand, being negative, de- posits on the positive pole. Chlorine and so- dium deposit respectively on the positive and negative poles. In order to prevent the accu- mulation of oxygen and hydrogen, contrivances are provided, which continually wash the sur- faces of the anodes to prevent polarization, which would stop the whole process. With regard to chlorine, it has been established by Beguerel that chlorine in its nascent state is more active than afterward, so that if in the ore under treatment any gold is present, it would now be almost readily attacked by the chlorine and form itself into chloride of gold (Salt Of COldl Which apain IN nlllhl in nrafor The gold being now "in solution !s readily acted upon by the electric current. The mole- cules, as established by Grotthus, 1805, are un- der the same condition as any other molecules, which in their transit to the negative zone be- come split up into their elements, the chlorine parting and returning to the positive zone, while the gold is deposited on the negative pole in a fine metallic condition in the inner cham- ber. From this it is washed and drawn off in the contracted part of the inner chamber, in conjunction with the caustic soda, and passed through a filter. The powder is then calcined, and the gold remasses. The gold having been extracted from the ore, the latter is drawn off at the bottom of the outer eel), and an equal amount entering simul- taneously at the top from a hopper, in which it has been mixed with the salt, makes the action continuous. In a working plant, every ton of ore will be virtually from 20 to 24 hours under the chlorinating and electrical influence, and travel about 20 feet, which will give sufficient time for effective treatment. As to the cost, it is estimated to be about one-ninth of the present cost of chlorination, or that three shillings five pence per ton should cover the cost of supervision and sinking fund for capital. The inventor RBtimates the outlay for a complete plant to be 250, exclusive of an engine to drive the dynamo. THE old IT SID REGISTERED OFFICE OF THE COMPANY: COLLINS STREET WEST. * 'ERGUSSON AND MITCHELL, COLLINS STREET WEST. ijx! JoVIV THE IT IE ID. REGISTERED OFFICE OF THE COMPANY: 49 COLLINS STREET WEST. MELBOURNE : FERGUSSON AND MITCHELL, COLLINS STREET WEST. J. COSMO NEWBERY. J. E. GARD. EDWARD WOODS. J. L. MORLEY. C. W. CHAPMAN. Semfarj, F. H. C. COOK. CLAUDE VAUTIN. Ifogtsiereb Office. 49 COLLINS STREET WEST. Morhs, MELBOURNE. (LIMITED.) THE Directors of the above Company desire to bring under the notice of the mining community a New Gold Extraction Process. This process is an improvement on the well-known Plattner's chlorination process, the principle of which is, converting the gold in the material under treatment into a soluble chloride, and in such form removing it from the ore as a solution in water, and precipi- tating the gold from the solution thus obtained. The principle of the Plattner process has received the warmest support from metallurgists during the past thirty years ; but the practical difficulties and trouble of applying it, the slowness of operation, and the difficulty of removing the solution of gold from the ore, together with the cost of treatment, has prevented the general adoption of the "chlorine " or Plattner process for the extraction of gold, Being fully aware of the value of chlorine as a means of extracting gold, if it could be applied in a rapid, cheap, and effective manner, Messrs. Newbery and Vautin were led to investigate the subject, and they have devised the Improved Chlorination Process, by which they claim that, by 4 THE NEWBERY-VAUTIN GOLD the adoption of the discovery of Plattner, and the practical application of the improvements suggested by De Lacy, Hears, and others, with ideas of their own, to have produced a perfect gold extraction process. In order that the following description of the improved process may be fully understood, it is necessary to briefly describe, in somewhat elemen- tary terms, the principle of " chlorination," and how it is applied in the old and improved process. "If contact takes place between gold and chlorine, the two elements combine, and form a definite compound, chloride of 'gold, which is very soluble in water ; and in this form the gold can be removed from the material under treatment by washing, or leaching it with water, and as before stated, the gold can be obtained from such solution by precipi- tation." Now, in order to apply the above principle in the Plattner or old chlorination process, the following modus opercmdi is followed :--The material for treatment, after having been rendered practically free from sulphur, arsenic, antimony, &c., by roast- ing, is first damped, an operation requiring great care, as the ore must not be too wet or too dry, if good results are to be obtained. It is then sifted into a large vat, and chlorine gas from a generator is forced below a false bottom, and allowed to rise up through and permeate the ore in the vat ; this requires many hours to effect. A lid is then placed on the top of the vat and luted down, and the whole allowed to remain from fourteen to forty- eight hours, as circumstances may direct. When the workman believes that the chlorine has com- bined with the gold, the lid is removed and water introduced on to the surface of the ore, to dissolve the chloride of gold formed, and the solution allowed OO / I 7 EXTRACTION COMPANY (LIMITED.) 5 to drain off through a filter-bed on the false bottom of vat, and run into a vessel, where the precipitation of the gold is effected. This washing or filtering operation requires from twelve to twenty-four hours. In the event of the ore containing slimes, or being too fine, it cannot be filtered at all, in which case chlorination by old method has to be abandoned as means of treatment. The solution containing the gold is then treated with a reagent, generally sulphate of iron, and the chloride of gold is decomposed and the gold pre- cipitated in a finely divided metallic form, and slowly settles to bottom of vessel ; this generally takes from ten to twenty hours. The precipitated gold is then collected, dried, and melted. The above brief description is sufficient to enable a comparison to be drawn between the old and new process ; but if further information of Plattner's process is required, reference may be made to standard metallurgical works. From the above remarks on the old method of chlorination it can be easily understood why the objections, slowness of operation, and consequent high cost are continually urged against its applica- tion ; great skill is also necessary to obtain anything like practical results. Slimes cannot be operated on, and only material containing gold in the finest state of division can be treated, for should the gold grain be coarse it is in a short time protected from the action of the chlorine by being surrounded by chloride of gold ; or if the gold is of low standard, alloyed with silver, it is protected by a film of chloride of silver, and under such conditions con- tinual washing and repeated treatment would have to be resorted to : the time and expense of such operations thus prevents the application of chlorine under the old method to such ores. 6 THE NEWBERY-VAUTIN GOLD In the new process the improvements are of such a character that not only are the mechanical difficulties of the old method overcome, but the chemical reactions are greatly accelerated, the cost reduced from about 1 10s. to 12s. per ton, and the loss of gold made practically nothing ; in fact, a slow, uncertain, costly, and cumbersome process, has been converted into a rapid, economic, and effective means of extracting gold from auriferous pyrites, refractory ore, tailings, &c., from which, when necessary, antimony, sulphur, arsenic, &c., have been removed by proper calcination. The new process will be readily understood by the following description and reference to the plan herewith : The material for treatment is deposited in the hopper " A " over the chlorinator " B," which is a rotating vessel constructed of such material and in such a manner that chlorine has little or no effect on it, and strong enough to withstand an internal pressure of 60 Ibs. per square inch. The chlorinator " B " is charged with from 20 to 30 cwt. of ore from the hopper " A " by allowing it to fall into it through a manhole ; a given quantity of water, chlorine, or chlorine-producing chemicals is then added, the manhole cover is securely placed in position, and the vessel is then perfectly gas-tight. A pipe leading from the air pump " " is connected with a valve on the chlorinator, which is opened, and an air pressure produced as required or found necessary, depending on. the coarseness of the gold (the effect of this air pressure will be explained further on;) the valve is then closed, and connection with the air pump broken. The vessel, with its contents, under pressure, is caused to revolve for one hour, when it is stopped, and a EXTRACTION COMPANY (LIMITED.) 7 pipe connected with the valve, which leads into a closed vessel or vessels " D," in which there is lime or soda water ; the vessels " D " are connected with the vacuum pump of special construction, so that when the valve on the chlorinator " 3C$is opened, any chlorine that may exist in the form of gas is drawn into the lime or soda water in " D " and absorbed ; by this means the workmon are pre- vented from inhaling any chlorine gas, which would be the case if the surplus chlorine is not withdrawn before the chlorinator is opened. After a few minutes the cover to the manhole of the chlorinator is removed, and the vessel again put in motion, when the contents are discharged into the vessel " E " called the solution separator or filter, which consists of a lead-lined iron vat with a false bottom, and connected with the vacuum pump " G " by the pipe " F." Immediately the contents of the chlori- nator are deposited in the solution separator, the communication between the vacuum pump and filter is opened, and the solution of gold chloride rapidly withdrawn from the ore, and deposited in holder "H." Water is continually- added to the surface of the ore in the filter, and the solution from it tested from time to time, and when found free from gold, the connection with the vacuum pump is broken and the filter tipped up, and the waste ore or tailings fal] into the truck " I," and are run out on to the tailings heap. The removal of the gold solution and washing of the ore occupies, with ordinary sands, about one hour, no matter how fine; when large quantities of slime are to be treated, extra filters must be provided. The solution of gold in the holder " H " is then allowed to flow through charcoal in vessel " J," during which passage the chloride of gold is decomposed, and the gold deposited on and in the 8 THE NEWBERY-VAUTIN GOLD charcoal, which when fully charged is burnt, and the ashes fused with borax in a crucible, and the gold obtained. In places where water is scarce the liquid from " J " can be used over and over again, with economy, as it becomes charged with hydrochloric acid, which assists in liberating chlorine in the chlorinator. It can be pumped up to cistern " K " for further use. The lime or soda water in the vessels " D " can also be used to produce chlorine for fresh charges of ore after it has combined with the chlorine drawn into it, just before opening the chlorinator as before described above. Having thus briefly noted the operation in the new process, we will point out some of the advan- tages of it, 1st. It will be observed that the material for treatment falls by gravity into the chlorinator. and is not damped or sifted by hand as in old method, for it does not matter how wet it is ; thus a great saving of time and labour is effected at the very beginning of the operation. 2nd. That the vessels in which the chlorination takes place do not occupy much space, say 4 feet by 5 feet, instead of siy 10 feet by 10 feet, as required by the old vat process. 3rd. That the ore under treatment is kept in motion during the time it is exposed to the action of the chlorine under pressure. The great advan- tages of combined motion and pressure are, that the combination of the chlorine with the gold under this high pressure is far more rapid than when under the normal atmospheric pressure ; and no matter how large or coarse the gold grain may be, O07I7 EXTRACTION COMPANY (LIMITED.) 9 it is rapidly dissolved ; there is no obstruction to the action of the chlorine on the gold grain by being surrounded with a solution of gold chloride, or coated with silver chloride, as pointed out as a source of failure in the old process, for a fresh surface of each grain of gold is being continually exposed to action of the chlorine, in consequence of the mechanical cleaning of the grain by the ore being in constant motion. In cases where the silver alloyed with the gold is worth recovering, or any that may be present as chloride, it can be obtained by adding salt to the charge, when, as is well known, it will go into solution. This is a point of great importance, and makes the process of value, and applicable when the gold exists alloyed with high percentage of silver, as in New Zealand and some Australian mines. A great point of value, and to which special attention is directed, in the improved process, is the introduction of compressed air, for by such means any chlorine that would otherwise exist over the sur- face of the ore, in the form of gas, is forced into the water with which the ore is mixed in the chlorinator. By this means there is not only a great saving of chlorine, but the chemical action of it is greatly accelerated, and the gold in the ore converted into a chloride in one hour or so, instead of fourteen to forty-eight, as in the old process. Another point is, that in consequence of the short time the material under treatment is exposed to the action of the chlorine, many of the difficulties experienced in the old process are not encountered. 4th. The time saved in separating the solution of gold from the material is one of the principal features of the mechanical improvements of the new process, for heretofore the difficulty of leaching, 10 THE NEWBERY-VAUTIN GOLD or washing the ore, and thereby removing the solu- tion of gold chloride, has been one of the great drawbacks to chlorination. The rapid filtration is brought about by means of a vacuum produced under the filtering medium in solution separator, by a specially constructed pump, the action of which prevents the material, however fine, from settling down on or into the filter-bed in a compact mass, but, on the contrary, keeps the same lively and open, 5th. The advantage of decomposing the gold solution by passing it through charcoal or other insoluble reagents are numerous, and will be fully appreciated by those who have experienced the never ending and uncertain method of precipita- tion by sulphate of iron ; and, moreover, such a means of recovering the gold is practically auto- matic, and risk of loss by theft may be reduced to a minimum. 6th. The cost of the plant, apart from motive power, buildings, and any calcining furnaces that may be required, is about per set of two chlorinators or barrels, with pressure and suction pumps, &c. When small quantities, say fifty tons or less per week, of ore are to be treated, the process can be worked in one barrel or chlorinator, but great economy will be experienced in using them in sets of series of two or more, as the pumping power for exhaust and pressure with the smallest effective pump for one chlorinator or barrel, is the same as required for four or more. The plant is so constructed that additional sets can be added when required. The capacity of each barrel or chlorinator is from fifty to sixty tons per week. EXTRACTION COMPANY (LIMITED.) 11 7th. The plant can be made to treat small or large quantities of ore, and can be set up on remote mines, as to the cost is quite within the means of working miners raising ten to twenty tons per week of auriferous ores, pyrites, &c., and no great skill is required to work the new process, as all the details have been so arranged that any per- son of ordinary ability can master the working of process in all its parts in a few days. The process is in full work at the celebrated Mount Morgan Gold Mine, Queensland, and it is worthy of remark that every other known method of gold extraction, including the old chlorination, was practically tried by the proprietors, but with- out success, when the rapid chlorination was intro- duced with such marked success, that the loss in the tailings is not (1 dwt.) one pennyweight per ton. Its practical application to refractory ones has been ensured by the success obtained at Norton, Queensland, at the mine of Messrs. Conran and Co. Norton ores contain copper, zinc, lead, sulphur, and arsenic. The United Pyrites Company, Sandhurst, where the old chlorination process plant exists, as well as the latest amalgamation appliances, are erecting with all speed a plant to work the new process. The cost of chlorination proper is from 10s. to 12s. per ton, including labour and wear and tear ; the chemicals required amount to about 2 % of the ore treated, and can be so packed that no trouble or risk need be experienced in transit, and the acid necessary may be obtained dry in wooden casks. Any plants ordered may be made under the direct supervision of the Company's Manager, and tested and stamped before leaving the foundry. 12 THE NEWBERY-VAUTIN GOLD EXTRACTION CO. (LTD ) The Company will also, when desired, make arrangements for starting the plants, and instruct the Working Manager, &c. The Company are erecting a test plant in Mel- bourne, and will be prepared to treat small test lots of ores, &c., so that mine owners and others may be guided by actual results. Particulars as to cost of treating trial lots, and other information, may be had upon application to the Secretary, 49 Collins Street West. Fergusson and Mitchell, Printers, 27 Collins Street West, Melbourne. OO7 i y RETURN ENGINEERING LIBRARY 642-3339 LOAN PERIOD 1 2 3 4 5 6 ALL BOOKS MAY BE RECALLED AFTER 7 DAYS Overdues subject to replacement charges DUE AS STAMPED BELOW MONOGRAPH SEplp 1978 N)K UAit DUE Sf tOAN SfHFnm r UNIVERSITY OF CALIFORNIA, BERKELEY FORM NO. DD11, 12m, 3/78 BERKELEY, CA 94720 O07I7