r 
 
 REESE LIBRARY 
 
 UNIVERSITY OF CALIFORNIA. 
 
 Jl&<2/*&w 
 
 Accession No. / ^/ / 9 . Class No. 
 
 
 a^oB^v^^ 
 
 5m 
 

 I 
 
 
 . 
 
 
 
' 
 
HINTS 
 
 ON- 
 
 AMALGAMATION 
 
 AND THE 
 
 GENERAL CARE OF GOLD MILLS 
 
 BY 
 
 W. J. ADAMS, A. M., E. M. 
 
 i 
 
 Graduate of the School of Mines of Columbia University, 
 New York. 
 
 A REFERENCE BOOK OF ACTUAL GOLD-MILL PRACTICE, 
 DETERMINED BY AN EXPERIENCE OF TWENTY YEARS 
 WRITTEN IN LANGUAGE THAT CAN BE 
 UNDERSTOOD BY ALL. 
 
 ILLUSTRATED. 
 
 CHICAGO: 
 MODERN MACHINERY PUBLISHING COMPANY. 
 

 Entered According to Act of Congress in the Year 1898, 
 
 BY W. J. ADAMS. 
 In the Office of the Librarian of Congress at Washington, D. 0. 
 
 19//9 
 
TABLE OF CONTENTS. 
 
 Page. 
 
 Introduction 7 
 
 Chapter 1 General Process 11 
 
 Arrangement of Mortars 17 
 
 " Plates 21 
 
 " " Concentrators .... 30 
 " for Canvas Plant .... 34 
 
 " 2 Care of Quicksilver v *. \ 35 
 
 Amalgamation 43 
 
 " 3 Cleaning-up 60 
 
 4 Retorting and Melting 73 
 
 " 5 Concentration 85 
 
 6 Sampling 98 
 
 7- Conclusion 108 
 
UNI". Y 
 
 INTRODUCTION. 
 
 Gold has been known from the earliest ages, from its 
 occurrence in a metallic state in sedimentary deposits 
 as well as in veins. On account of its great specific 
 gravity, it can be collected from placers and river beds, 
 by separation with water alone, and in veins after the 
 matrix is crushed, a great amount is saved by the same 
 simple method. When only rich deposits were exploited, 
 anybody could manage as it apparently required only 
 labor and opportunity, while as long as money was 
 made, the losses that occurred did not trouble the own- 
 ers. From this very simplicity of working, the major- 
 ity of owners and investors imagined that no special 
 training was requisite to insure success, but that any 
 trustworthy man, skilled in mercantile pursuits, was 
 the proper person for the place of general manager. 
 To-day the same opinion is held by very many, in spite 
 of the warnings from hosts of disastrous failures. One 
 cause for this belief has been the lack of literature for 
 this special branch of metallurgy; in fact, very near 
 1890, there was practically no works written at all 
 which spoke of gold except as a subsidiary product 
 of the metallurgy of other metals. Volumes, both prac- 
 tical and scientific, have been published which deal with 
 the special branches of the metallurgy of lead, copper, 
 
 7 
 
8 HINTS ON AMALGAMATION. 
 
 and silver, but the metallurgy of gold seemed so simple, 
 it only required an occasional article in a paper or 
 magazine. 
 
 In spite of this dearth of written knowledge, practical 
 men in all parts of the world were rapidly improving 
 the methods of treatment, both mechanically and with 
 the aid of chemistry, in their several localities; but, 
 through lack of exchange of thought, each section had 
 a different process, on which faith was pinned to the 
 exclusion of all other processes. 
 
 As the rich deposits gave out, attention was turned 
 to those of lower grade, which are now found to be very 
 profitable with improved machinery and increased 
 knowledge, but, even to-day, we are in the infancy of 
 this science. The treatises on gold, now before the 
 public, can still be counted on the fingers of one hand, 
 and are either devoted to the scientific discussions of 
 processes now in vogue, the history past and present 
 of gold milling, or the mechanics pure and simple of the 
 various machinery used. They are all good for the edu- 
 cation of the world, but are lacking in definite direc- 
 tions of the best way to employ the methods they 
 describe, and are generally understood by those only 
 who have enjoyed a previous technical education. This 
 absence of intelligent application of these known prin- 
 ciples in the great majority of the mills in this State 
 (the home of gold milling), has been a constant source 
 of wonder to me, and yet I have a fellow feeling from 
 
" HINTS ON AMALGAMATION. 9 
 
 my first experiences in gold-mill practice. Graduating 
 from a celebrated school of mining engineering, I 
 thought myself eminently fit to at once assume the 
 absolute management of the biggest mining concern on 
 earth, but, thanks to the kind influence of an elder 
 brother, already well known in the mining world, 1 
 was started at the bottom of the ladder in a gold mill, 
 to begin my real education. I very soon found that 
 there was no bigger tenderfoot in California, as my 
 technical education had only taught the chemistry and 
 scientific mechanics in general, with no practical rules 
 of how to apply this knowledge. These practical rules 
 have been learned through bitter experience, extending 
 through many years, and to try and help others who are 
 just beginning, I have set down in the following pages 
 the results of the observations I have made, all of which ' 
 have been practically demonstrated as correct by appli- 
 cation on several very difficult ores, with marked suc- 
 cess in every case. It has been a work of pleasure to 
 contribute this mite of knowledge, and if I am instru- 
 mental in increasing the production of only one gold 
 mill, I will feel amply repaid for my labor. 
 
 I ask the indulgence of the reader, to overlook the 
 absence of rounded sentences and polished language, 
 and take the will for the deed. I have done the best 
 I am able, and can only leave the verdict to the public. 
 
 W. J. ADAMS, E. M. 
 
 San Francisco. 
 
CHAPTER I. 
 GENERAL PROCESS. 
 
 It is not the purpose, in this book, to enter into any 
 detailed description of "gold milling," as the ground has 
 already been amply covered by E. B. Preston, in his re- 
 port on "Gold Milling," published by the "State Min- 
 eralogist," of California. 
 
 Some other points also may seem too well known and 
 appreciated to be mentioned, but these require con- 
 stant repetition, and even then very little practical ap- 
 plication seems to be made by the average millman. 
 Q[n order clearly to understand the entire method, we 
 must start with the ore as it comes from the mine. This 
 ore must first be carefully examined, as its character 
 and structure as well as its value, determine the most 
 advantageous method to pursue. First, the ore may be 
 hard and tough, requiring force to disintegrate it, though 
 entirely free-milling; second, the ore may be soft, giving 
 a great deal of slimes; third, the ore may be a mixture 
 of the above two divisions. 
 
 First: Here, the ere is first dumped over a grizzly, 
 with the bars set 1% inch apart, the coarse lumps going 
 through a rock-breaker of some form, to mix with the 
 fines in the ore bin. From this bin it must be carried 
 to stamps, preferably of heavy weight, notwithstanding 
 all assertions to the contrary by patentees and makers 
 of other pulverizing devices which are "just as good as 
 stamps." 
 
 Second: When the ore is soft, it also requires to be 
 passed through a breaker, to enable the particles to be 
 
 11 
 
12 HINTS ON AMALGAMATION. 
 
 of uniform size; but here, very frequently any kind of 
 stamp, and always those of heavy weight, will slush 
 through the bed of pulp, wearing out iron uselessly, and 
 increase the proportion of slimes, always to be avoided 
 as much as possible. Here we find a great advantage in 
 the different types of the Chilian mill, such as the Hunt- 
 ington and Bryan, from both of which the pulp escapes 
 as soon as it is reduced to the requisite size, as de- 
 termined by the screen, and with the minimum- of slimes 
 to hinder future operations. 
 
 Third: In an ore containing both soft, clayey or talcose 
 material, and hard bunches of quartz, stamps are gener- 
 ally the best, as the grit of the hard quartz prevents 
 pounding of iron on iron, and causes sufficient splash to 
 keep the screens from choking, while all operations can 
 be kept under close observation, which cannot be done 
 with any pan or roller mill one of the greatest objec- 
 tions to the general use of these mills. In some few 
 cases, however, where the output from the mine is suffi- 
 ciently large to w r arrant the outlay of capital, it will be 
 found of great benefit to separate the ore partially and 
 automatically into two classes. Dumping the ore over 
 a long grizzly, the soft and fine will go into one bin, 
 while the coarse, after being put through the breaker, 
 falls into a second bin. That from the first bin is fed to 
 one or more roller-pan miJn, while the hard broken 
 quartz goes to the stamp mill, very largely increasing 
 in this way the output through the two methods com- 
 bined. 
 
 The pulverized ore, technically known as "battery 
 pulp," is now carried by water down silver-plated copper 
 plates, by which means as much of the gold as possible 
 is abstracted, varying very considerably under different 
 millmen's methods; a low percentage saved, being ex- 
 
HINTS ON AMALGAMATION. la 
 
 cused by such terms as "floured gold," that floats in 
 water, rusty gold, "plumbago in the ore," or a similar 
 state of affairs. 
 
 However, there is generally sufficient gold left in this 
 pulp, which could never be saved with quicksilver, to 
 require further treatment, while the value is too low to 
 treat all the pulp en masse. This gold is either, me- 
 chanically or chemically, locked up with other metal- 
 liferous substances, generally sulphides or minerals of a 
 higher specific gravity than the accompanying gangue. 
 
 This specific gravity is the keystone to all the con- 
 centrating devices, and the special method required is de- 
 termined by only two facts, the value of the concentrates 
 when pure, and the percentage of them carried by the 
 ore. Should these concentrates be of low value and mod" 
 erately coarse, a simple bumping table, like the Gilpin 
 County bumping table, or its improvement, the Wilfley, 
 could be used, as they require little care, are reasonable 
 in price, and save concentrates free from foreign mat- 
 ter, while the final tailings, though still carrying a large 
 percentage of mineral, will be economically valueless 
 owing to the intrinsically low value of the sulphurets. 
 When, however, the concentrates are of value, for in- 
 stance above $50 per ton, a mechanism of much greater 
 delicacy must be employed, and of all the devices, none 
 has proved so satisfactory as an endless moving belt, 
 shaking without a jar. As a rule, the higher the grade 
 of sulphurets the more friable they are, and the finest 
 slimes, most easily affected by agitation, carry the rich- 
 est particles, reaching a culmination in the tellurides. 
 Should the "battery pulp" carry a high percentage of 
 sulphurets, that is, above 12 per cent., it very often be- 
 comes necessary to use a double concentration, and in 
 this case two machines of the same type are used, the 
 
14 HINTS ON AMALGAMATION. 
 
 tailings from the first passing directly to the second, 
 after removing the surplus water if there is too much 
 added on the first machine. 
 
 In spite of all these precautions, it is very frequently 
 found that the concentrator tailings still carry an ap- 
 preciable value, and most thorough tests must be made 
 to determine whether or not this can be economically 
 saved. The first and commonest method is to allow the 
 tailings to run over a large surface, covered with canvas, 
 which is cleaned and swept several times a day, but, 
 generally, this only saves a small percentage of the loss, 
 and its only advantage is its cheapness. With proper 
 care and experience the concentrators should save all 
 that the canvas plant could do, and any further reduc- 
 tion must treat economically with the entire mass. 
 
 So far the only way to do this is by employing some 
 of the modifications of the "cyanide process," and this 
 requires a large tank capacity, so that the tailings can 
 flow directly to the filtering tanks.J 
 
 This is concisely the method of gold milling, but there 
 are several points to observe, to insure complete success 
 on the majority of ores. 
 
 First, foremost and at all times is the question of 
 grease. Guard against its excessive use day and night, 
 month and year. Keep all the bearings and machinery 
 where it is used as scrupulously clean as a New En- 
 gland housewife does her home; do not grudge the use 
 of clean waste, but see that the employees observe the 
 maximum of cleanliness. Bits of candles do no harm, 
 or very little, if made of stearic acid, but beware of 
 tallow dips. Start in with the rock breaker, and place 
 dripping pans underneath the journals, making frequent 
 examinations to see that all the drops are caught. See 
 that none of the oil used on the running gear of the 
 
HINTS ON AMALGAMATION. 15 
 
 self -feeders drops on the feeder floor, being very careful 
 about working the leakage of ore always found under- 
 neath the feeders, if there is the slightest possibility 
 of its being fouled. Clean the stems of the stamps, the 
 cams and tappets very frequently, and do not use liquid 
 oil on them, but make a swab of blanket and apply a 
 minimum of axle grease, to the cams several times a 
 day, to the stems only as needed. When applied to the 
 stems, only touch them above the guides. It is gen- 
 erally better to tack some canvas between the cam- 
 shaft floor and the top of the lower guides, giving to it 
 a decided belly, to prevent any grease thrown by the 
 cams from falling into the feeder or throat of mortar, 
 or on the plates. In one mill, where very poor work 
 had been done, though the builder and superintendent 
 claimed most thorough knowledge, we found boards 
 placed below the cams to prevent the grease from falling 
 on the plates, and set at such an angle that there was a 
 constant rolling of pellets of grease directly into the 
 throat of the mortar. 
 
 We now come to the concentrators, and it can be safely 
 stated, with hardly an exception, that the cleanliness of 
 the machines is a sure indication of the quality of work 
 done, and the closeness of saving accomplished. 
 
 Where rubber belts are used, the oil rots them, the 
 sand and grit get into the bearings, causing bumping, 
 inequality of the plane of the table, and a little grease 
 getting into the pulp will prevent the saving of the finest 
 and richest of the sulphurets. The very act of cleaning 
 the machines brings all parts under close scrutiny, and 
 many a serious break-down is averted, observed in time 
 during this cleaning at regular intervals. Therefore, be 
 sure and watch for grease, daily caution the employes 
 about it, spare no pains nor expense to have every part 
 
it; 
 
 HINTS ON AMALGAMATION. 
 
 Modern Machinery. 
 
 t'ia. 1. 
 Copperplate. 2 Iron strip. 3 Wood backing. 
 
HINTS ON AMALGAMATION. 17 
 
 of the mill at all times as if on parade, and the close 
 saving and freedom from break-downs will amply repay 
 all the trouble and outlay. 
 
 Within certain limits the shape of the mortar does not 
 affect the economic results nearly as much as has been 
 supposed that depending mostly on the man attending 
 to them. A mortar must be narrow, as the object is 
 to get the ore out of the battery as fast as crushed. The 
 back should be curved from the throat, so as to throw 
 the ore directly on the center of the "die." This back 
 must be solid metal, and on no account have copper 
 plates in the back. Their advantage is very dubious, 
 and in nine cases out of ten their use is a very great 
 detriment to successful work. Without them the copper 
 plates on the "chuck-blocks" catch as much amalgam as 
 both combined; there is less surface to scour, particular- 
 ly with low-grade ore, and with them the additional 
 width of the mortar prevents the splash being exerted 
 exclusively against the screen, and reduces the crushing 
 capacity of the battery. (See Fig. 1.) 
 
 The discharge, that is, the distance between the top 
 of die and bottom of screen, should be within a fraction 
 of four inches, new dies requiring wooden strips under 
 the screens to keep this height. The "drop" of the 
 stamps should be 4y 2 to 5 inches, and the speed always 
 above 95 drops per minute, preferably above 100 drops. 
 A slow drop, besides decreasing the duty of the stamps, 
 allows the quicksilver to settle and diminishes its com- 
 minution so that too much is liable to be used at one 
 time, a sure loss if the gold is floured. A quick, short 
 drop more nearly approaches the action of the pan in 
 pan amalgamation, keeping all the pulp in constant 
 agitation, and mixing the quicksilver uniformly, so that 
 all parts of the ore come in contact with it before leaving 
 the battery. 
 
18 HINTS ON AMALGAMATION. 
 
 The "chuck-block," covered with the copper plate, 
 should be entirely separated from the strip of wood on 
 which the screen rests. The plate should touch the bot- 
 tom of the screen itself, at as slight an angle as possible, 
 and should be very nearly vertical and five inches deep. 
 Its backing, generally of wood, must be as slight as 
 possible, so as to place it far from the dies. It is held 
 
 FIG 2. 
 
 FIG. 3. 
 
 Nodern Machinery. 
 
 FIG. 4. 
 
 in place by a strip of iron, which extends into the shoul- 
 ders on each side of the mortar. 
 
 Two chuck-blocks should be made with the blocks to 
 conform to the height of the screen as the dies wear 
 down, as with dies half worn the wooden strip under- 
 neath the screen is removed, bringing the discharge 
 down to normal height, and the copper must not project 
 above the bottom of the screen-discharge. 
 
 This sketch, made without a scale, as the width of 
 mortars varies, will better explain it. Figure 2 shows 
 both cross-section and longitudinal section. 
 
HINTS ON AMALGAMATION. 19 
 
 The screens (see Fig. 3) are preferably made with open- 
 ings eight inches highland the entire length of the rnor- 
 tar. Abstain from putting any cross-pieces, which ob- 
 struct the freedom of discharge. In placing the screens 
 the chuck-block is first put in place, then the strip of 
 wood on which the screen rests, having a lining of 
 blanket tacked to both edges, and this strip of wood 
 is keyed by the shoulders cast on the lip of the mortar. 
 Then the screen is put in place and keyed by the wedges 
 driven down the shoulders on each side of mortar. There 
 still remains a large opening between the top of screen 
 and the bottom of the upper casting of the mortar itself. 
 This should be wide enough, even with new dies, to al- 
 low of the easy insertion of the arm to the shoulder. In 
 most mills this is very foolishly closed solidly by a 
 wooden false screen and keyed as tightly as the screen 
 itself. The proper way is to take a strip of wood the 
 full outside width of the mortar in length, and 2x1 
 inches, and on this tack very strongly either extra-heavy 
 canvas or a piece of rubber belting, which just fills the 
 opening in width and extends a little below the upper 
 edge of screen-frame, in depth. The advantages of this 
 should be obvious, but a few of them may be named: 
 First, it permits the inspection of the interior of the bat- 
 tery at all times, without stopping the stamps; second, 
 the cleaning, twice daily, of all accumulated chips and 
 other clogging of the inside of screen; third, the exami- 
 nation by touch of the amalgam accumulating on chuck- 
 block; and, fourth, in many cases, the driving on and re- 
 placing of shoes without removing the screen. 
 
 The greatest advantage of all is that the mill is stop- 
 ped as little as possible, and hence the most perfect 
 amalgamation maintained, while no hard amalgam is 
 broken away, as always occurs when the screen is re- 
 
20 HINTS ON AMALGAMATION. 
 
 moved. In fact, as my first great point was "avoid 
 grease," my second is, "Never remove the screen of a 
 battery till the run is ended, if it can possibly be 
 avoided, and the finer the gold the more important this 
 is." 
 
 It takes a very appreciable time, after a battery is 
 started, no matter how short the stop may be, before all 
 the pulp is in constant agitation, and the quicksilver 
 mixed with it. 
 
 This rule also brings us to the proper material of 
 which to have the screens made, and in this as well as 
 everything else, the best is always the cheapest. Theo- 
 retically, wire screens expose the most discharging sur- 
 face, but they clog the quickest, and have to be removed 
 to be cleaned by a wire brush, a very serious fault, as 
 stated above. Round-punched holes present too much 
 dead surface, being exactly the reverse of the wire 
 screens. This only leaves us the "burr-slot" and the 
 "punched-slot," and of these the burr-slot, though clog- 
 ging the least of any, wears coarser more quickly than 
 the punched-slot. Therefore the advice we give is to 
 use in stamp batteries "punched-slot screens," of the 
 best material to be had. Of material we have tinplate, 
 Russia iron and steel. Tinplate is the cheapest, but the 
 screens are worn out within a few days, and are really 
 the most expensive in the results that can possibly be 
 employed. Russia iron will not break easily, but the 
 orifices wear so coarse within 48 hours, particularly on 
 hard quartz, that the ore will not be pulverized as fine 
 as required. This leaves us only the steel, which breaks 
 before it wears coarse, on account of its hardness. Of 
 course there is steel and steel, but if a point is made 
 about it, steel screens can be procured which will not 
 break for over a month under rough usage, and even in 
 
HINTS ON AMALGAMATION. 21 
 
 that time the size of the apertures has not appreciably 
 increased, i. e., sufficiently to cause any loss in free gold. 
 
 Here we have the best condition, the battery in steady 
 operation for a month, the pulp in steady and constant 
 agitation, no disturbance of the hard amalgam, by re- 
 moving a screen; and the greater the quantity of amal- 
 gam in the battery, the more of the fine and floured gold 
 is caught there. Therefore use a "steel, punched-slot 
 screen," of the size found by experiment to be the best. 
 Several factors determine this size. 
 
 With coarse gold this is not of so much moment, but 
 should the gold be fine, it is necessary to crack the ore 
 that much more to free it. This degree of pulverizing 
 depends on the grade of the ore, as in many cases it costs 
 more to save the finest gold than the total amount saved, 
 and it then becomes necessary in practical reduction to 
 use a larger sized screen, put through more rock, and 
 pay little attention to additional loss in the tailings. 
 However, it is best to use as fine a screen as is conform- 
 able with a profit in working the mine. 
 
 The outside of the screen must be scraped several 
 times a day, and as good a device as any is a copper 
 spade with the edge turned over at an angle of 45 de- 
 grees; wooden handle, copper riveted, as shown in 
 Fig. 4. 
 
 There should be a long expanse of copper-plate surfacs 
 below each battery, though some of it is only of use in 
 case of faulty amalgamation. 
 
 These plates are technically divided into: 
 
 INSIDE COPPER CHUCK-BLOCK, a description of 
 which has already been given, and there is only to add 
 that it is an unnecessary expense to have it silver-plated. 
 
 LIP-PLATE, which must be heavily silvered, at least 
 three ounces of silver to the square foot being put on it. 
 
22 HINTS ON AMALGAMATION. 
 
 This plate is just the length of the mortar and is wide 
 enough to extend from the inside-edge against which 
 the bottom of screen is braced, to a half-inch beyond 
 the iron lip of mortar. Two rectangular holes are cut 
 in it, to allow the shoulders of lower keys to project, and 
 the wooden strip on which the screen rests is placed on 
 top of the plate and holds it solidly in position. 
 
 SPLASH PLATE. This is rarely found, even in the 
 
 10" "8" 
 
 Modern Machinery. 
 
 best mills, but is of the utmost importance; the more so, 
 as the gold is floured. In fact, it is absolutely necessary 
 if very fine gold is to be saved. It should be 12 inches 
 wide, by a length just sufficient to fill the space between 
 the shoulders of the mortar. There are several ways of 
 adjusting, but in every one the point to be observed is, 
 
HINTS ON AMALGAMATION. 23 
 
 that it shall stand in front of the screens at an angle 
 never less than forty-five degrees and better if over fifty 
 degrees from horizontal; that the bottom shall be at 
 least an inch below the bottom of the screen, and the 
 space between the screen-frame and it shall not exceed 
 three-quarters of an inch. Take this plate and fasten 
 it to an inch board, leaving a margin of the board below 
 the copper plate, to act as a brace to the stalactites 
 slowly formed, and then by back supports, stand it on 
 the edge of the next plates, so that it is held firmly 
 against the mortar and yet can be instantly removed, 
 as shown in Fig. 5.. 
 
 Another way of great simplicity, which, however, has 
 the objection of causing too much jar, is to rivet a piece 
 of track iron on each shoulder, at the angle the plate 
 shall stand, and slide the plate down, keeping it away 
 from the screen by a false strip tacked to the front of 
 the board, along each side of the plate itself. 
 
 By studying the effect of this its advantages can easily 
 be seen. Twenty years ago it was universal to have 
 a spray of clear water constantly dropping on the apron- 
 plate to form a slight stoppage of the pulp and cause the 
 amalgamated gold to settle and attach itself to the plate, 
 but, as future working of the pulp was very much hin- 
 dered by this excess of water, it is now rarely used. 
 Again, to a certain extent, the output of the mill is in- 
 creased the greater the amount of water allowed to flow 
 into the battery, and as a result, all the water that could 
 be used and not hinder future operations, is allowed to 
 run into the mortars. 
 
 No matter how fine the gold may be, if it is free, under 
 proper amalgamation, it will adhere to an amalgamated 
 surface if brought into actual contact with it, and this 
 the splash-plate does in two ways. First, half of the 
 
 OF THE 
 
24 HINTS ON AMALGAMATION. 
 
 pulp is thrown against it in a coarse spray, aiding adhe- 
 sion by the force; second, it then runs down the plate, 
 dropping off the bottom exactly similar to the spray from 
 the clear water troughs used in earlier times, forming 
 a dam and eddies, which cause the other half of the pulp 
 to precipitate its fine amalgam at this point. 
 
 From here, the object to be attained is to have no rap- 
 id and strong currents. To turn the pulp over and over, 
 so that all parts are frequently brought in contact with 
 the amalgamated surface, and to spread this pulp as 
 thin as consistent with keeping it in constant motion and 
 allowing no settling of even the heavy sulphurets on the 
 plates. It is also found that an occasional drop of one 
 inch to one and one-half inches is a benefit. 
 
 Now we come to one of the greatest mistakes made by 
 90 per cent, of all amalgamators, an error held to like 
 the grip of death by men of broad technical education, 
 causing the failure of many properties which should be 
 successful. 
 
 This is the grade given to the large plates. These 
 should never be placed with less than 2y 2 inches to 
 each foot, and in most cases 3 inches would be better, 
 and even more, while better work can be done at an 
 angle of forty-five degrees than with a grade less than 
 2% inches. 
 
 Take a case where the plates are set below 2y 2 inches, 
 we find an excess of water required to keep all the pulp 
 moving and, therefore, too great a depth, so that the 
 fine gold is held in solution and never touches the amal- 
 gamated surface, when we truly have float gold, while an 
 equally bad feature, almost universal, is that it allows 
 too much quicksilver to be used, and fine gold will never 
 be saved with even a slight excess of quicksilver. This 
 point will be more fully explained under the discussion 
 of amalgamation. 
 
HINTS ON AMALGAMATION. 25 
 
 With the plates at the proper grade and the requisite 
 amount of water, the pulp travels down the plates in 
 a succession of waves, the lower edge of each wave 
 rolling over and over and bringing every particle of 
 water even, in contact several times with the amalga- 
 mated surface. The more sulphides the ore carries, the 
 steeper must be the grade of the plates, to clear them and 
 still not interfere with the concentration of the tailings. 
 
 After this explanation we can continue the descrip- 
 tion of the plates. 
 
 From the lip-plate the pulp has a drop of nearly two 
 inches and falls on the first plate separate from the mor- 
 tar. 
 
 The apron-plate should be divided into two sections, 
 the first easily removed at all times. This should be the 
 full length of the mortar, and two feet wide, and that 
 end nearest the battery resting on the wooden shelf fast- 
 ened to wooden mortar-block, and held in place by the 
 lip of the mortar or a strong hook on each side, while the 
 lower end rests on the second section. This second sec- 
 tion must have the same width, and be from 4 to 6 feet 
 long. It is supported by extension legs firmly secured to 
 the floor. By using this form of support the grade of the 
 table can be changed to suit the ore, after practical ex- 
 periment. Start with a grade of '^ to 3 inches, and, if 
 too much water is required to keep all the pulp in steady 
 motion, lower the second section (the first assuming the 
 same grade, as it rests on it), until the pulp is seen to 
 move freely and in successive waves with a minimum of 
 water. 
 
 On most ores this amount of plate surface is all that is 
 necessary, but if there is still sufficient fall to allow the 
 tailings to be readily carried away automatically, the 
 pulp is now passed over "sluice plates," as a safeguard 
 
26 HINTS ON AMALGAMATION. 
 
 against accidents, after passing through a quicksilver 
 trap. - | * i|i'J 
 
 These sluice plates are 18 inches wide and from 8 to 
 10 feet long, and are set at a minimum angle of 1% inch 
 per foot. All the plates should have a coating of silver 
 of three ounces to every square foot, although on the 
 sluice plates two ounces will do. 
 
 There are several devices for traps, but most of them 
 are only receptacles where a slight obstruction to the flow 
 of the current is given and this is not enough. We 
 want to accomplish two objects: first, retain all the 
 amalgam and quicksilver that may have escaped the 
 copper plates; second, secure this with a minimum of 
 sand and sulphurets. 
 
 A large open box is always filled with sand which is 
 gradually replaced by coarser sand and sulphurets ac- 
 cording to the length of time before its complete re- 
 moval, while only a modicum of loss is arrested here. 
 The next result of experimenting caused the pulp to de- 
 scend on one side and rise on the other of a partition, 
 the higher specific gravity of the valuable portions aid- 
 ing their retention, and it is on this principle, that the 
 most successful traps are now constructed; the best of 
 all being those used in the mills of the "Homestake" in 
 the Black Hills, and designated as the "Black Hills 
 Trap." 
 
 This can easily be constructed of wood by any good 
 carpenter, as it consists of a wooden box with sheet 
 iron partitions, loosely set in grooves cut in the sides 
 of the box. A trap for five stamps is given here. It is 
 made of V/ 2 inch clear lumber; inside measure horizon- 
 tally 10 inches wide by 8 inches; depth at inlet, 18 
 inches; at outlet, 6 inches. Plough three grooves equally 
 distant in each side and *4 inch deep, making them 
 
HINTS ON AMALGAMATION. 
 
 27 
 
 wide enough to allow a sheet of heavy iron or copper to 
 slide readily up and down. The middle groove should 
 extend clear to the bottom of box while the other two 
 are stopped 2 inches from the bottom. 
 
 Fig. 6 shows the details of construction of box, a 
 perspective view and the method of attaching handle 
 to the middle partition. 
 
 The first iron or copper plate is cut 10% inches wide 
 and 18 inches long, with a handle riveted to its upper 
 
 \ 
 
 \ 
 
 Modern Machinery. 
 
 edge. The second is cut 10% inches wide and 12 inches 
 long, with a rod riveted at each side and extending up 
 4 inches, as shown in cut. The third is like the second, 
 10%xl2 inches, with a handle riveted on its upper edge 
 like the first. 
 
 Here we have at two separate times 6 inches' pressure 
 to force the pulp, the first time a vertical distance of 12 
 inches, the second time a distance of 6 inches, both prac- 
 tically prohibiting the escape of a metal of such a 
 
HINTS ON AMALGAMATION. 
 
 high specific gravity as quicksilver, even if very finely 
 comminuted and still not enough to prevent the escape 
 of all the pulp and sulphurets except a slight layer less 
 than two inches, which also is in constant agitation as 
 
 f >ox 
 
 Modern Machinery. 
 
 long as the same amount of water is employed. Should 
 this water get slack from any cause, the first division 
 at once becomes choked, but the trap is quickly freed 
 
HINTS ON AMALGAMATION. 29 
 
 by raising the first partition. When the trap is cleaned 
 all the partitions are withdrawn and the residue, very 
 small in quantity, is removed. 
 
 The pulp, on leaving the apron-plate, falls into a 
 box with the bottom sloping from each side to a central 
 vent, from which it flows directly into the trap, and on 
 leaving the trap, either flows over the sluice-plates, or, 
 
 Modern Machinery. 
 
 in their absence, into wooden or iron launders, to be con- 
 veyed to the concentrators. Fig. 7 shows two cross-sec- 
 tions of the box in front of apron-plates. 
 
 The battery tailings, after leaving the sluice-plates, 
 or, if they are absent, the amalgam trap, fall directly into 
 the concentrating launders. These are preferably made 
 of wood, as iron pipes, if choked by broom straws, 
 pieces of blanket, etc., have to be disjointed to be cleaned. 
 These wooden boxes, troughs or launders measure inside 
 4 inches wide by 6 inches high, and must have at the 
 very least a grade of % inch per running foot. Now, 
 under the most careful management, a little amalgam 
 and quicksilver escapes all the devices mentioned above, 
 and it is advisable to put in a couple of "riffles" in each 
 box length of 12 feet. This is done in this way: Before 
 the bottom piece is nailed to the sides, make a saw-cut at 
 right angles to the length equally distant and a half inch 
 deep, and then gouge out to it from the upper side. This 
 is shown in Fig. 8. 
 
 If the water used is always the same in quantity, a 
 V-shaped box will carry the sand with the smallest 
 
30 
 
 HINTS ON AMALGAMATION. 
 
 amount, but should the water slacken at all the sand at 
 once makes a broader surface and then from the in- 
 creased friction and breadth the launder is at once filled 
 to the top. To gain some advantage from the V-shaped 
 form we have found great benefit in putting angle strips 
 
 . s 
 
 Modern Machinery. 
 
 along each side of the box, 1 inch wide and 1 inch high, 
 giving a 2 inch bottom with flaring sides, as shown in 
 Pig. 9. 
 
 When the pulp is divided over two machines a division 
 with a long swinging finger is put in and each launder 
 reduced to a width of 2 inches, from the end of which it 
 is carried by a rubber hose to the concentrators. 
 
 THE CONCENTRATORS. As stated in the beginning, 
 all sulphurets of a value above $50 per ton require a 
 shaking table with an endless belt that must work 
 without a jar, and be at all times completely under the 
 control of the operator. 
 
 Two classes of machines are in vogue, one shaking 
 sidewise or across the stream, the other with an end- 
 shake against and with the stream. Years of practical 
 experience have proved that the end-shake concentrators 
 cannot produce concentrates free from foreign matter, 
 
HINTS ON AMALGAMATION. 31 
 
 though in some cases the tailings have a very low valu- 
 ation, while any attempt to make clean headings results 
 in excessive loss. This can readily be seen as the up- 
 stroke against the current exerts too great a force against 
 the clear water regulated for the downstroke, while if 
 regulated with sufficient force to keep the sand back on 
 the upstroke, it washes down the finer and lighter sul- 
 phurets during the downstroke. This has been acknowl- 
 edged by the inventors of the end-shake machines, from 
 the fact of the universal application of the side-shake 
 since that special patent has expired. 
 
 The first of these side-shake machines is still taken 
 as the standard, being superior in the estimation of the 
 world in its operation and ease of adjustment, and far 
 ahead in the quality of material employed in its con- 
 struction. This makes it, however, the most expensive 
 at first cost, though the cheapest in the end. This is 
 known as the "Frue Vanner," and the general applica- 
 tion of all being the same, it will be taken to illustrate 
 the general method of concentration. However, we wish 
 first to explain the reason for the use of a wooden frame, 
 to which some objection is made. It is this, that there 
 is sufficient spring to a wooden frame to prevent any jar 
 to the table as it is thrown an inch each way, and this 
 jar is always very perceptible on all the machines resting 
 on a rigid iron frame. 
 
 We will now continue the course of the battery tail- 
 ings. The concentrator is set with a grade regulated by 
 screws at the foot, up which and against the cur- 
 rent the endless belt travels, and this grade is arranged 
 so that there is at all times a thickness of pulp of ^ 
 inch which is neither stiff nor sticky. The speed of the 
 shaking motion for average ores is started at 190 revo- 
 lutions per minute, and then the proper grade is deter- 
 
32 HINTS ON AMALGAMATION. 
 
 mined only after actual experiment. The pulp falls on 
 the machine near its upper end, being uniformly distrib- 
 uted by the "ore-spreader" over the entire width of 
 the belt. On this ore-spreader it is well to have a silver- 
 plated copper plate, as this is the last opportunity to 
 catch separately any amalgam or quicksilver that may 
 have escaped all the other devices. 
 
 The ore-spreader must deliver the pulp to the belt with 
 as little splash as possible so as not to disturb the sul- 
 phurets that have already settled. To do this there 
 should be a step added, as shown in Fig. 10, to break 
 the fall, and this step must just clear the surface of the 
 pulp already on the machine. 
 
 In front of this ore-spreader is placed a clear water 
 distributer, which supplies just enough water to sepa- 
 rate the remnants of sand from the sulphurets, and take 
 the place of the water coming down with the pulp. 
 The water should be just enough to keep all the field be- 
 tween the water distributor and the ore-spreader cov- 
 ered with water without a current. Too little water is 
 shown by a series of dry fingers against which the finest 
 sulphurets shake, become dry and float down the ma- 
 chine uncaught. Should some sand come up with the 
 sulphurets and no dry fingers be exposed, do not turn on 
 more water, but either decrease the speed of the uphill 
 travel of the belt if the bed of pulp is the right depth 
 and not sticky, or give the machine a steeper grade by 
 lowering the foot. The tailings from the concentrators 
 under proper management should show by panning tests 
 no more sulphurets, though perhaps an assay by fire 
 will still show that too much is being lost, either in sul- 
 phurets too finely slimed to be collected by hand tests 
 or in tellurides, oxidized minerals or carbonates. Very 
 often these fine slimes can be saved with coarse canvas, 
 
HINTS ON AMALGAMATION. 
 
 Ore >--^c/<?^ 
 
 fig. II 
 
 r/g.i2 
 
 .&",.. 
 
 5- 
 
 C- 
 
 Modern Machinery. 
 
84 HINTS ON AMALGAMATION. 
 
 requiring very little additional expense except the first 
 outlay in erecting the plant. We can safely say that m 
 ninety-nine per cent, of these cases all the value is in 
 the slimes, so that our first duty is a mechanical separa- 
 tion or sizing. This separating is done with the well- 
 known "spitz-kasten," a V-shaped box divided by a par- 
 tition. Here the coarse sand is drawn out through a 
 hole at the point of the V, while the slimes overflow at 
 the top, clear water being added to help the separation. 
 The cross-section in Fig. 11 will explain the principle. 
 
 The slimes and water are now carried in launders to 
 the canvas plates, always made in duplicate to allow the 
 cleaning of one set while the slimes are flowing over the 
 other. The cleaning is done with a broom and in some 
 cases a spray of clear water under pressure. The tables 
 are made of matched lumber, varying from 4 feet to 12 
 feet wide and 10 feet long. They are set at a grade of 
 1% inches for each running foot, and are covered with 
 No. 6 canvas. As stated above, the tables must either be 
 made in duplicate or, in a large plant, a couple of extra 
 tables are provided, to be used while cleaning those i-n 
 steady use. The slimes and water flow down one series 
 of tables for a definite time, generally one to three hours, 
 when the pulp is turned off and a small amount of clear 
 water is used to carry off a little of the waste. Then a 
 tilting board is placed under the foot of the table and 
 the concentrates swept and washed into the settling 
 box. The concentrates, if rich enough, are shipped with- 
 out further handling, but it is found occasionally to be 
 of benefit to reconcentrate them over a machine set with 
 very little grade, and running at a very low speed. We 
 show in Fig. 12 the method of saving the washings of 
 the canvas plates, as generally adopted In California. 
 
CHAPTER II. 
 CARE OF QUICKSILVER, 
 
 It is generally acknowledged that special care must 
 be exercised to keep the quicksilver absolutely pure and 
 lively, and the advice given is to retort it, as that will 
 eliminate all the impurities. This is a fallacy, because 
 there are certain elements which will vaporize with 
 the quicksilver and still contaminate it, so that even after 
 retorting we find it necessary to resort to chemical agen- 
 cies to establish its highest efficiency. We buy a flask 
 of quicksilver from the producers, and generally find 
 it absolutely pure, but at times the mass will separate 
 into globules which have a repellent power, one on the 
 other. This is probably caused from the use of lime 
 in the retorting of metal from its ore of cinnabar. 
 Lime has a peculiar effect on quicksilver, as a slight 
 addition to sluggish metal, separated into globules 
 will not only liven it up but cause the globules to 
 join together, while an excess will increase more than 
 fourfold the repellance of the globules toward each 
 other. Therefore, we must suppose the fresh unused 
 quicksilver is contaminated by too much lime. Two 
 chemicals are open to our use, both of which will destroy, 
 pound for pound, an equal amount of the quicksilver, 
 viz., a strong solution of cyanide of potassium, or a 
 weak one of nitric acid. Now, nitric acid causes fuming, 
 and renders the millman susceptible to salivation, so 
 that it is better to use cyanide, if possible, in all our 
 operations of cleansing. 
 
 35 
 
86 HINTS ON AMALGAMATION. 
 
 When the practical adaptation of the solubility of gold 
 in cyanide of potassium became generally known, the 
 majority of millmen, and more especially the owners 
 of mines, were afraid to use any cyanide in their opera- 
 tions, as they believed they were liable to lose much of 
 the fine gold in the ore, dissolved by the cyanide. This 
 is a very erroneous impression, except in a case where 
 cyanide in solution was mixed with the ore previous 
 to the introduction of quicksilver. In other words, cy- 
 anide of potassium has the greatest affinity for grease 
 and copper, and will also dissolve quicksilver, if present, 
 without affecting the gold at all. This enables us to 
 use this chemical in conjunction with quicksilver to 
 great advantage in all our operations. Always, then, 
 before using any of the quicksilver, add to it a solution 
 of cyanide, and a strong solution is better than a weak 
 one; in fact, we have used a saturated solution with 
 benefit. Some of the quicksilver is poured into a china 
 bowl and the surface is covered at least to a depth of 
 one-half inch with the solution, with which it must 
 always be kept covered. As each spoonful of quick- 
 silver is fed into the batteries it is thoroughly brightened 
 and cleansed in passing through the supernatant liquid, 
 and is in the best condition to catch the gold. After 
 the quicksilver has been in use in the mill, it is fre- 
 quently spoiled by certain elements in the ore, or some 
 accidental fouling, such as the heating of a journal and 
 the consequent flowing of babbit metal into the ore-bin. 
 From the elements in the ore, we find lead, tellurium, 
 and selenium. The worst fouling, however, comes from 
 babbit metal. This turns the quicksilver black, mak- 
 ing it slimy and frothy. In this case retorting of the 
 quantity contaminated must be resorted to, but a partial 
 help can be had by using sulhpnric acid, allowing the 
 
HINTS ON AMALGAMATION. 37 
 
 fuming to go on for several hours, with occasional stir- 
 ring. The loss is very great. Should the ore contain 
 tellurium or selenium, it will always be found neces- 
 sary to purify the quicksilver after retorting, as these 
 metals are carried over with the quicksilver in distill- 
 ing the quicksilver from the amalgam. Here we must 
 employ nitric acid, allowing it to fume for several hours. 
 Then, after washing thoroughly, a solution of cyanide is 
 added, turning the liquid black. On removing this with a 
 sponge, the quicksilver is found to be in perfect condi- 
 tion. Some advise the addition of a small amount of 
 sodium amalgam to the quicksilver, but personally we 
 are very averse to using it on account of its causing even 
 the iron of the mortar to be amalgamated, while the 
 amalgam on the plates is kept too soft. 
 
 Turning then to the room especially set apart for 
 chemicals and quicksilver, and specifically known as the 
 clean-up room, we need to keep in stock all our supplies, 
 which consist of the following list: Commercial cyanide 
 of potassium, O. P. nitric acid, C. P. Sulpuhic acid, 10 
 pounds of copperas or sulphate of iron, 10 pqunds of 
 blue-stone or sulphate of copper, some pieces of soft 
 chalk for lining the retort, a heavy horseshoe magnet, 
 a 40-mesh screen 18 inches in diameter for sieving wood- 
 ashes, a mortar, and pestle of one quart capacity and 
 one of two quarts, two gold pans and one copper bottom 
 pan, two white enameled iron pails, two porcelain lined 
 kettles with bales, of one gallon capacity and two of 
 half gallon, several pint and quart stoneware bowls, 
 and several cups without handles, a large carriage 
 sponge and several smaller sponges, a few yards of fine 
 canvas, one-half dozen whisk brooms of better quality 
 than the ordinary clothes brushes, a couple of scrubbing 
 brushes, one-half dozen hand whitewash brushes, a 
 
HINTS ON AMALGAMATION. 
 
 u 
 
 Modern Machinery. 
 
HINTS ON AMALGAMATION. 39 
 
 couple of square rubber scrapers, or, what is better, new 
 rubber belting with sharply cut edges, having at least 
 a dozen already prepared, and a small platform scale 
 for weighing the quicksilver and amalgam. This should 
 use avordupois weights, as it is only the bullion itself 
 that is weighed in troy ounces. 
 
 Make the floor of matched lumber, on top of the reg- 
 ular flooring, with a tightly fitted baseboard all around 
 the room, remembering that quicksilver is very elusive 
 and disappears from no apparent cause. This room is 
 placed to one side of the battery floor with one win- 
 dow that commands a full view of the batteries on 
 one side, and a window letting in light from the outside, 
 directly in front of the clean-up tank, while the door, 
 secured by a padlock, leads from inside the mill and 
 never from the outside, so that all persons before get- 
 ting to this important room must pass before the obser- 
 vation of the mill employees. A ground plan is given in 
 Fig. 13. 
 
 The work-bench is made of 2-inch lumber, with solid 
 legs that will not jar the room when heavy hammering 
 is done. On this old screens are removed from their 
 frames and new ones put on, and as there is always 
 some amalgam attached to the old screens, the top of 
 the table must be tight so that the residue can be col- 
 lected and planned. The implements required, each of 
 which should have its place just above the table, are, a 
 light hammer, a steel scraper (home made, either from 
 an old file or a putty knife), a tack extractor, a pair of 
 snips or tin shears, and a punch to enable the tacks to 
 enter the steel. The only tacks of any account are 
 those known as upholstery, ordinary carpet tacks in- 
 variably losing their heads, while small wire nails are 
 held too firmly by the wood for subsequent withdrawal 
 
40 HINTS ON AMALGAMATION. 
 
 on replacing the screens. The punch is made of steel, 
 similar to a scratch-awl, or according to Fig. 14. There 
 must also be here, ready to hand, a piece of blanket of 
 good quality and strips of wood of various sizes, for 
 patching a hole in a screen temporarily, when it is not 
 advisable to remove it just th^n, as, for instance, during 
 the night when nearing the end of a run, with so much 
 amalgam inside the battery that, to save any further 
 dispute, it will be as well only to open the battery in 
 the presence of the party who is directly responsible. A 
 stock of screen frames with ne\v screens on and ready 
 for use must always be kept on hand, and this reserve 
 should never be less than three, as in no instance is the 
 old adage so exemplified of "time being money" than 
 the moments lost in stopping a battery from its work. 
 In putting the new screens on the frame, be sure that 
 the rough side, presenting the smallest openings is on 
 the inside. 
 
 The cupboard must be arranged to be kept under 
 lock and key, be fitted with shelves on which all the 
 supplies, scrapers, chemicals, assortment -of wire nails 
 and quicksilver are kept, but no oil or grease must be 
 allowed in this room. 
 
 In arranging the tray and panning tank, we must 
 get the best light possible on our work, and therefore 
 they must be placed in front of the window on the out- 
 side of the building. The tank must be 4 feet 6 inches 
 by 2 feet on top and tapering to the bottom, where the 
 dimensions are 4 feet by 18 inches. It must be 2 feet G 
 inches deep. Six inches from the top is placed an over- 
 flow pipe, discharging outside the building into a sluice 
 a few inches wide, either set with riffles or covered with 
 a copper plate, while a drain hole, stopped with a plug, 
 is bored just above the bottom. A slat is tacked along 
 
HINTS ON AMALGAMATION. 41 
 
 each side, a foot from the top, on which a movable 
 wooden grate can Ibe placed, to rest a pan while breaking 
 up the lumps, or a screen that requires washing. 
 
 On the left side, and projecting an inch over the tank, 
 is placed the tray solidly built and absolutely Avater- 
 tight. This should be 4 feet 6 inches long, and at least 
 18 inches wide, have a bottom preferably of one piece 
 of l^-inch clear lumber, having edgings 2 inches high on 
 three sides, and open in front of the tank with a gutter 
 along this open side to collect any quicksilver that may 
 run down. The slope should be ^-inch to each foot. 
 Over this tray must be placed a clear-water pipe, V 2 or 
 %-inch, fitted with a globe valve and a piece of rubber 
 hose 12 to 18 inches long. This is explained in the sketch 
 of Fig. 15. 
 
 On this tray the chuck blocks are scraped and all the 
 amalgam put through its final cleaning. The scrapers 
 are made from old files of all lengths and shapes. One 
 edge is hammered flat and ground to a chisel edge, 
 while the other end is bent to nearly a right-angle before 
 it is ground. Shown in Fig. 16. 
 
 The brooms are improved by a small scraper inserted 
 in the handle, as shown in Fig 17. 
 
 Be sure and keep a large stock of file scrapers, sharp- 
 ened and ready for use, always on hand, but also keep 
 them all under lock and key till wanted in cleaning up. 
 
 We will now start with a mill newly built and note 
 the final preparations necessary before the run is begun. 
 We put a half inch of dry sand in the mortars and 
 place the dies, the sand being required to act as a cush- 
 ion to the .blows of the stamps to prevent the cracking 
 of either the mortar itself or the dies. Then the shoes 
 are placed on top of the dies, the shank being sur- 
 rounded with soft pine wedges tied on with a string. 
 
42 HINTS ON AMALGAMATION. 
 
 In case the mill is a very large one, say of 40 to 80 
 stamps, much time is saved by preparing this circle of 
 wedges beforehand. It is done in this way: A shoe is 
 taken and the wedges placed around it, and then a 
 strip of cloth is stretched over them and fastened to 
 each wedge with a tack. This circle is then withdrawn 
 and a sufficient number made for all possible use. After 
 that, it is only necessary to slip one of these circles 
 over the shank of the shoe, and it is at once ready. 
 After the shoes are ready they are driven on singly, 
 by the power employed, a board being placed between 
 the shoe and the die, to eliminate any danger of chipping 
 the iron. They are then hung up by the fingers on the 
 cam shaft floor. The chuck-block is taken to the clean- 
 up room and amalgamated. First, it is thoroughly 
 scoured with a weak solution of nitric acid till the true 
 color of pure copper is shown. Then washed with a satu- 
 rated solution of cyanide of potassium and quicksilver 
 sprayed from a bottle over the mouth of which a piece of 
 canvas has been stretched. The quicksilver is rubbed into 
 the copper by the exertion mainly of "elbow grease," as- 
 sisted by a cloth and sand, but it must be very thor- 
 oughly attached to the copper, the surplus being re- 
 moved by one of the "rubbers." The splash plate and 
 lip plate are also dressed in the clean-up room and the 
 operation with them is that which is employed on all the 
 remainder of the plates. They are first thoroughly 
 scoured with cyanide of potassium and then the quick- 
 silver is sprayed over them and rubbed hard with a 
 cloth, avoiding all the use of sand or grit of any kind. 
 Cyanide of potassium is added frequently until the en- 
 tire surface looks not only bright but wet. Then the 
 surplus quicksilver is again squeezed out with the rub- 
 bers and the plates are ready for use. 
 
HINTS ON AMALGAMATION. 43 
 
 The lip plate is now placed in position and the chuck- 
 block keyed to its place and the first section of the apron 
 plate is fastened to the mortar block. Broken ore, both 
 fine and coarse, is now thrown into the mortar and 
 packed around and over the dies to a depth of 2 to 4 
 inches, when the screen is put in place and the splash 
 plate attended to the last of all. The water is now 
 turned on from two cocks, one on each side of the bat- 
 tery and directly over the tops of the stamp-heads. Two 
 streams are better than one, as it enables us to regulate 
 the proper quantity of water, and also, by increasing 
 the amount on one side or the other to keep the duty of 
 each stamp uniform. Until this water has reached the 
 bottom of the trap do not drop a stamp and then only 
 one battery of five at a time, till it is perfectly under 
 control, both in regard to the feed of ore and the uni- 
 form drop of the stamps. At first no quicksilver is 
 added on account of the excess that is on all the cop- 
 pers, from the preliminary amalgamation. A good deal 
 of this will be carried away by the attrition of the sand 
 and the jar from the battery within an hour, when we 
 can begin to regulate the proper amount and interval 
 of time to feed quicksilver. On average ore we begin 
 with a drop the size of No. 4 bird shot, and as the out- 
 side plates gradually get drier, gradually increase the 
 amount fed each time till we find the plates to keep 
 the proper color. All our determinations are made on 
 the splash plate, lip plate and the first few inches of the 
 apron plate. 
 
 It is very hard to put on paper the proper color ana 
 consistency of amalgam on the plates, but we will do 
 the best we know how. The amalgam on the splash 
 plate and lip plate must be kept hard and dry or very 
 little amalgam will remain there. The first four inches 
 
44 HINTS ON AMALGAMATION. 
 
 of the apron plate must also be dry, hard and immov- 
 able to pressure by the finger, while below it gradually 
 should become softer, and, when pushed by the finger, 
 have the consistency of putty; while at the very bottom 
 of the apron a similarity to thick molasses is not too 
 soft. The color of all must not be dull, like frosted sil- 
 ver, nor as bright as quicksilver alone, but nearly ap- 
 proaches the appearance of a looking glass. Of the two 
 extremes, however, the dull frosted appearance is far 
 preferable, as quicksilver is always being carried by the 
 attrition of the sand and where quicksilver goes there 
 is lost also the fine gold held in solution. The finer the 
 gold, the drier must be kept the plates, the less quick- 
 silver put in at one time and the shorter the interval 
 between the additions of the feed into the mortars. If 
 too much quicksilver is added it is at once noticed from 
 the small amount collected near the battery, and its 
 accumulation increasing as it travels down the plates. 
 When the plates are kept in proper shape near the battery 
 the proper wetness can be controlled at all times, on the 
 lower part of the apron, by an occasional sprinkling of 
 quicksilver, and this will attract the last of the flour 
 gold that may have escaped previous amalgamation 
 without jeopardizing the gold already amalgamated and 
 collected in and near the battery. 
 
 Even to-day some people advocate only outside amal- 
 gamation, putting no quicksilver at all into the battery, 
 but we believe that as much gold should be caught in- 
 side the battery as possible and for flour gold especially 
 the highest efficiency is attained with dry amalgama- 
 tion in the battery and a soft but not wet amalgamation 
 on the lower apron plate and the sluice plates. Even on 
 ore that runs nearly the same in value, day in and day 
 out, constant watchfulness and observation of the condi- 
 
HINTS ON AMALGAMATION. 45 
 
 tion of the plates must be exercised and it is generally 
 advisable to examine each plate with the aid of a very 
 small stream of clear water each time any quicksilver 
 is to be added. Sometimes a touch of the finger is suf- 
 ficient to inform the adept, but this takes a long time to 
 acquire, so as to place any trust in it. In addition to 
 observation of the outside plates, daily feel the chuck- 
 block, by removing the canvas over the screen and in- 
 serting the arm very carefully. As each watch of men 
 will remove the chips, etc., before quitting time, of 
 course without stopping the mill, they can then feel the 
 chuck-block, see that everything is fastened properly, 
 that the amalgam is accumulating, and has the proper 
 touch and hardness. The touch of amalgam should not 
 be slippery, neither should it be sandy. It must show 
 a uniform hard, dry, and solid surface on the chuck- 
 block, splash and lip plates, but can be moved into a 
 pasty ridge on the apron plate. In regard to the interval 
 of time to allow between the feeding of the quicksilver 
 several factors must be considered. All gold is only 
 amalgamated on its surface, and, therefore, coarse gold 
 requires less quicksilver per value than fine gold, which 
 presents a larger area per unit of value, and, in addition 
 to this, the finer the gold the more frequently the quick- 
 silver must be -added. If it is found that the size of the 
 grains of gold in the ore have diminished rather than add 
 the necessary addition to the regular dose reduce the 
 interval of time one-half, or as found most beneficial. 
 
 We generally expect 011 average ore, i. e., $8 to $10 
 of moderate coarseness, to feed quicksilver once every 
 hour, but if very fine and floured, once every half-hour 
 is not too often. The superintendent must allow some 
 discretion to his amalgamators, as even on ore of very 
 uniform quality it is not politic to give an order for a 
 
46 HINTS ON AMALGAMATION. 
 
 certain feed of quicksilver for more than two hours, 
 and, therefore, it is very necessary that thoroughly com- 
 petent men alone be employed in this capacity. 
 
 We feed the quicksilver and know it is in its best 
 condition, but our* labor is lost unless we keep it in that 
 condition as far as possible all the time. Our watchful- 
 ness has prevented its contamination by grease and yet, 
 in many cases, even after only a few hours' run, we 
 find the plates coated with various colors that would 
 sicken any subsequent amalgam or quicksilver, so that 
 it will not be attached, but flows on to waste. This 
 coating must be removed, even if thie mill is stopped 
 every three hours to "dress the plates." 
 
 If the amalgam is removed from the plates too fre- 
 quently or too close, the silver coating disappears very 
 rapidly and just as soon as the copper is exposed the 
 plates are always tarnished with verdigris, the colors 
 starting as a pale golden yellow, but rapidly becoming- 
 dark, greenish and brown. For this there are only two 
 remedies, one to remove the plate and have it re-sil- 
 vered, and the other, which we consider far better, to 
 amalgamate it with gold amalgam and be more careful 
 in the future from removing 'the amalgam so thoroughly. 
 First, clean and scour till the pure color of copper is 
 shown with cyanide of potassium, or a solution given 
 later. Then amalgamate with quicksilver, rubbing it in 
 thoroughly and then, after removing the surplus quick- 
 silver, take a little amalgam of floured go^u and coat the 
 plate thoroughly with it.- Afterward both in dressing the 
 plates and cleaning up, push the amalgam from other 
 parts of the plate to this spot until it is found to keep as 
 bright as all other parts. 
 
 With the ores of this State, California, we find a pur- 
 plish brown stain, caused by telluride of gold, a black 
 
HINTS ON AMALGAMATION. 47 
 
 or very dark brown, from selenide of gold, and a most 
 beautiful steel-blue sheen which comes from iridosmium. 
 These stains themselves are all rich in gold, and unless 
 saved at the time and place noted, will ^e mainly lost, 
 as they defy concentration, are apparently soluble in 
 water and, without special chemical treatment, are im- 
 pervious to the action of cyanide of potassium. It is, 
 therefore, useless for us to use simple cyanide, which, 
 though making the plates and quicksilver bright, would 
 allow all this scum to flow to waste. 
 
 There is one mixture, however, that helps us very ma- 
 terially, known to very few, as far as we are informed, 
 and only employed by the two or three possessing its 
 simple formula. Even where there is no special need for 
 its employment we always use it in preference to a sim- 
 ple solution of cyanide. It only consists of a mixture of 
 copperas and cyanide, forming a solution of both ferro 
 and ferri cyanide of potassium. 
 
 The preparation of this mixture has never been put 
 in an exact formula, and can either be made freshly 
 each day or in quantity. Our method has been to take 
 two quarts of water and add to it two to four ounces of 
 cyanide of potassium, and when this has partially dis- 
 solved, we add a pint of a saturated solution of copperas 
 and stir the mixture thoroughly; but on using this mix- 
 ture or part of it, we do not clean out the sediment until 
 necssary, but add at first fresh water and the next day 
 more of the different ingredients and fresh water as 
 needed. Crude, but satisfactory results are obtained. 
 The method of application is the same for the daily 
 dressing of the plates as well as to remove stains. The 
 stamps of one battery are hung up, then the water is 
 turned off and the concentrators attached to that bat- 
 tery are stopped, so as to keep their load uniform and 
 
48 HINTS ON AMALGAMATION. 
 
 lose as little of the sulphurets as possible. A stream 
 of clear water of considerable strength is now directed 
 first on the screens and then over the plates till all the 
 sand and slimes are removed. 
 
 Starting at the bottom of the first section of the apron 
 plate a whisk broom is dipped into the mixture and the 
 plate rubbed with a circular motion, of which the 
 strongest movement is upwards towards the battery 
 and carries the amalgam that way. This is repeated 
 until the entire section has been scrubbed with the mix- 
 ture and the whisk broom. The splash plate is then 
 tilted over and the mixture brushed lightly over it, and 
 afterwards the broom is drawn lightly over the lip 
 plate, but any amalgam disengaged is brushed to the 
 apron plate. Very little of the mixture has left the 
 plates and has been acting on the gold bearing stains 
 and the sulphurets which have been attached to the 
 plates by the particles of gold mechanically adhering to 
 them. The plates are now brushed up in a straight 
 line, and all the loose amalgam sulphurets, etc., are col- 
 lected into a small heap, when they are taken up with a 
 rubber and small iron scoop and put into a china bowl 
 which has some clear water in it. If the lower apron 
 is also stained, it is treated in the same way, but gen- 
 erally the stains are kept on the upper plates. Careful- 
 ness has been taken to disturb and remove as little of 
 the amalgam as possible, and most of it is saved in the 
 china bowl; but every time the broom is dipped into 
 the mixture a little amalgam is washed off into the 
 kettle; so that it must all be saved and once a week or 
 so, poured out and cleaned. The amalgam now lies on 
 the plates with microscopic ridges caused by the broom, 
 parallel with the current, and to change rhese to trans- 
 verse ridges, the whitewash brush is taken and drawn 
 
HINTS ON AMALGAMATION. 49 
 
 continuously across the plates, back and forth, till the 
 battery is reached, when the water in the battery is 
 turned on, the stamps are dropped and the concentrators 
 started. Generally this treatment is sufficient when 
 done at 7 a. m. and 5 p. m. each day, but as stated 
 above, should the plates again become stained, hang 
 up and dress them in this same way, even as often as 
 every three hours. On no account try to remove the 
 stains with the battery running and the sand passing 
 over the plates, as much amalgam is carried away and 
 the gold in the stains lost forever. Should the plates 
 require dressing every three hours, it is not necessary 
 to rub them so hard with the whisk broom, except in 
 the morning and evening, but this double dressing must 
 not be neglected, even if the plates are apparently clean 
 and bright. They always are improved by it, and with 
 practice ten to fifteen minutes is all that is required 
 on each battery. Whenever it is found that considerable 
 4 amalgam is collecting at the lower part of the plates, 
 brush it up with the broom towards the head of the 
 plates, and once a week lightly remove the surplus from 
 the lower apron and the sluice plates with a rubber, 
 but do not touch the amalgam on the splash, lip and 
 upper apron till the time for the general clean up of the 
 mill, as the thicker the amalgam that is there, the more 
 of the fine gold is caught and nearer to the battery as 
 well. It is also a fact that gold amalgam is less liable 
 to tarnish than any other amalgam. 
 
 We occasionally find another difficulty to contend 
 with, in that the gold is "rusty," that is, coated with a 
 film rendering its surface impervious to the attack of 
 quicksilver. This is of rarer occurrence than imagined, 
 as the loss of gold is very often laid to this cause, when 
 the gold is capable of being amalgamated if proper care 
 
50 HINTS ON AMALGAMATION. 
 
 and knowledge are employed. In some oxidized ores, 
 taken above water level, a laboratory test of amalga- 
 mating will show gold not touched by quicksilver, but 
 here the ore is first ground by itself and then the quick- 
 silver and water (and a good deal of water) are added 
 and it is shaken in a bottle or stirred in a wedgwood 
 mortar, after which the amalgam is separated by pan- 
 ning. In a battery with stamping, coarse gold is hit 
 and cracked and an inside bright surface exposed, 
 which is at once attacked by the quicksilver, present at 
 the same time, before it can again become tarnished; 
 while fine gold is ground temporarily bright by the vio- 
 lent agitation of coarse and fine rock thrown against 
 the sides of the mortar and the screen surface. In this 
 way a great deal of gold, reported as rusty, and not 
 available for amalgamating, is found to act very satis- 
 factorily when actually worked, while this result is 
 helped by the use of our sovereign mixture, the high 
 specific gravity of gold causing it to remain on the 
 plates mechanically, when it is taken up for future 
 treatment in our daily dressing of the plates. If we 
 know positively that we are dealing with rusty gold, 
 we can help ourselves a little by throwing into the bat- 
 tery every hour a piece of bluestone the size of a wal- 
 nut, but our principal work should be on the outside 
 plates. It is not a very good plan to put any cyanide into 
 the battery, as it may dissolve free gold before the 
 quicksilver has coated its surface or dissolved it. 
 
 After the dressing of the plates, the kettle, brooms, 
 rubbers, and bowl of amalgam and dirt, are taken to 
 the clean-up room; the rubbers and brooms are washed, 
 and then put away. If the mill is a small one, ten 
 stamps or less, the amalgam collected at one time is so 
 small, it is better to put the bowl away as it is, and only 
 
HINTS ON AMALGAMATION. 51 
 
 clean the amalgam when sufficient has accumulated 
 to warrant the time expended, remembering that the 
 chemical mixture is acting beneficially and more of the 
 gold is in condition to be recovered. If the mill, how- 
 ever, is 20 stamps or more, enough "muck" (it looks 
 like slimy .mud,) is daily collected to make an appre- 
 ciable quantity of clean amalgam, and this daily amount 
 requires closer manipulation than the large quantity 
 collected on clean-up day. When we find we have 
 enough, including that collected from replacing the 
 screens or any other source, we proceed in this way: 
 First, we have a bowl of quicksilver, kept specially for 
 this purpose and used over and over, because after the 
 first cleaning it has become charged with all the gold 
 it will carry in solution, and we then lose no more 
 from each subsequent daily bath of the new amalgam. 
 The collections from the plates, sulphurets and all, are 
 dumped into this quicksilver and thoroughly mixed with 
 the hand. The dross rises to the top, though a little 
 collects around the sides of the bowl and is mechanically 
 held on the bottom. Placing the bowl in a gold-pan 
 holding some water, we remove the dross and water 
 with a small sponge. After the surface is cleansed, the 
 sponge is pressed to the bottom and sides and all the 
 dross possible brought to the surface and removed, until 
 the quicksilver is bright and absolutely dry. This 
 quicksilver is then poured slowly into another bowl 
 half full of clear water, when most of the remaining 
 dross will be left attached to the sides of the first bowl, 
 and the balance will be floated on the second bowl from 
 which it is removed with a sponge. The dross, with 
 some amalgam, rusty gold and quicksilver, is now en- 
 tirely in the gold pan, ready for further treatment. This 
 is now put into one of the iron mortars and only a very 
 
52 HINTS ON AMALGAMATION. 
 
 little water kept, not more than a couple of tablespoons 
 full, as we require the mixture to be thick for proper 
 grinding. It is now ground for several minutes, in fact, 
 till it seems to be nothing but a slime, when the mortar 
 is placed in a gold pan, and a stream of clear water 
 under pressure is turned on, the mixture being rapidly 
 stirred with the pestle, till the water flows clear, over 
 the sides of the mortar. The surplus water, except a 
 very little, is then poured off, and the grinding renewed 
 until this clear water is dark and possibly has become 
 thick once more, when the operation of washing with 
 clear water is again employed. After this second wash- 
 ing there should only remain with the amalgam, the 
 iron from the battery and a little coarse sulphurets. 
 Leaving the water in the mortar the iron is removed 
 with the horse-shoe magnet and then the water re- 
 moved, when the amalgam collected can be carefully 
 added to that in the bowl, leaving the sulphurets behind 
 in the mortar. If this last amalgam still has a bluish 
 or brownish coating, it is a gold-bearing stain and 
 should be added to the general amalgam. The dross, 
 sulphurets, etc., are now put into the copper-bottom 
 pan, which has been amalgamated, shaken in this and 
 washed into the tank. 
 
 A piece of the fine canvas is taken and thoroughly 
 wet on both sides and then placed in a bowl of clear 
 water. Into this some of the quicksilver and amalgam 
 is poured, but only a quantity that can be handled con- 
 veniently, the canvas is twisted tightly and the quick- 
 silver squeezed through, adding the amount to it, until 
 either it is all in one ball or the ball is of a size not to 
 be cumbersome. Now, it is not necessary to exert great 
 strength to eliminate the last of the quicksilver, as more 
 can be extracted by rubbing the hand or the thumb, 
 
HINTS ON AMALGAMATION. 53 
 
 with a steady pressure over the ball, with frequent 
 immersions in the water, than by violent twisting. 
 When the amalgam is squeezed dry the canvas is laid 
 open on the gold-pan, the bottom covered with water, 
 the ball of amalgam pressed into solid shape, all de- 
 tached pieces added, and the ball is then rolled over 
 every part of the canvas. In that way it collects every 
 speck of amalgam, and has its surface smoothed with 
 the small amount of quicksilver remaining in the in- 
 terstices of the canvas, while any dirt or sulphurets is 
 kept from being attached, owing to the water in the 
 pan. Dry amalgam, even with a little free quicksilver, 
 becomes very hard in 24 hours, and the slight addition 
 of mercury to the surface of the ball, from rolling over 
 the canvas, acts as a cement to keep the ball together 
 in a compact mass. The canvas is washed in the pan, 
 squeezed dry and hung up. The floured quicksilver is 
 collected, rubbed by the finger into a globule and added 
 to that in the bowl. The ball is now weighed in avoir- 
 dupois ounces, and put into the safe or strong box, and 
 entered into the book for mill reports, as the product for 
 one day or number of days, as the case may be. 
 
 It may seem that this work is not required and that 
 the amalgam can be saved and cleaned with that col- 
 lected from the general clean-up, but it will be found 
 to be money saved, to attend closely to the instructions 
 given above, and particularly where we have to contend 
 with tellurides. The foreman of the mill, or the super- 
 intendent of a small plant, have ample time each day 
 to devote to this work; more gold will be acquired, and 
 the retort metal alone, in its cleanliness and the small 
 loss from the subsequent melting, will more than repay 
 the attention to the small details advocated. If this im- 
 perfectly amalgamated muck is roughly panned and 
 
54 HINTS ON AMALGAMATION. 
 
 the amalgam alone saved, the loss in a month is ap- 
 preciable, and it is forever gone, while this is the only 
 alloy of gold which is hard to clean, and not that from 
 the chuck-blocks or inside the battery. 
 
 We see the mint saving the dust on the roof, the car- 
 pets, and the clothes of the workmen, and getting a mar- 
 velous quantity of gold, and yet, in a mill, the amal- 
 gam, the scrapings and refuse are all handled as if of 
 no more value than the sand on the ocean beach. Lately 
 a report was made by a responsible consulting mining 
 engineer, that he estimated the value of an old mill 
 and the ground on which it stood, to be over $40,000.00 
 in amalgam, quicksilver and sulphurets, and it has been 
 our experience that in the majority of mills which have 
 been in operation for several years astonishing results 
 are obtained from scraping the cracks in the floor and 
 working over everything about the mill or under it as 
 well as the tail-sluice below the property. Save all the 
 chips, screen frames and any wood that has been in 
 use in the battery and sluices, burn them to ashes 011 an 
 iron plate and amalgamate the ashes. After the cast- 
 ings have become dry, examine them thoroughly, and 
 remove every speck of amalgam, even if some of the 
 iron is broken off with it. Hammer the old screens and 
 scrape off all the rust; while all small bits of iron, even 
 that saved by the magnet, should be mixed with salt 
 and dampened occasionally, and spread out in the sun 
 where it is exposed to the weather. Every six months 
 this is run through the clean-up barrel or clean-up pan, 
 whichever is employed. 
 
 The floor, on which are placed the plates, is given a 
 slope towards the concentrators, and at the end of this 
 floor a gutter is placed which will catch all the sweep- 
 ings and water that may flow down. This gutter must 
 
HINTS ON AMALGAMATION. 55 
 
 have a slight grade, ending in a wooden box or a pipe, 
 to carry off the waste, but in each gutter one or two 
 riffles a couple of inches high, are placed before the 
 overflow pipe is reached. Each morning the plate-floor 
 is swept thoroughly to this gutter, or in summer washed 
 down with the hose, and a stream of water of moderate 
 strength is occasionally run through the gutter, and the 
 concentrated material at the riffles removed. Every 
 leak from the plates is at once calked and stopped, as 
 where the sand goes some of the quicksilver and amal- 
 gam will go, even if a panning test might not show an 
 appreciable quantity. We can safely handle all the 
 dirt on this floor, as we have taken especial pains to 
 prevent any drippings of grease, coal oil, or other dele- 
 terious substances from coming in contact with the 
 plates or their environs. 
 
 One other question has properly to be considered, and 
 that is the temperature of the air, and the battery water, 
 in regard to its action on the amalgam. We see the 
 effect of heat in the expansion and contracton of mer- 
 cury in thermometers without changing the weight in 
 the least. We also find that our bowl of cleansing 
 quicksilver will have a very appreciable amount of 
 crystalline amalgam after the first cold night. There- 
 fore, we have these deductions to make: As the cold 
 increases, the quicksilver becomes more viscous and 
 slower in motion, and it will not dissolve amalgam, and 
 to increase the cold beyond a certain point the mass 
 is so lacking in its lively characteristic, that it will re- 
 quire more in quantity and with the least beneficial re- 
 sults. According to actual experience this temperature 
 prohibitive to good work is that of 25 degrees Fahren- 
 heit or lower. With an increase of temperature, the 
 quicksilver expands, becomes more fluent, runs easier 
 
56 HINTS ON AMALGAMATION. 
 
 and will carry much more fine gold in solution, and we 
 are enabled to keep more perfect control over our op- 
 erations. To any one accustomed to amalgamating 
 "wet," a low temperature will be of most benefit though 
 in no case will perfect work be done. In wet amalga- 
 mation the cold viscous quicksilver will form a pasty 
 mass, easily collected with a rubber, but as soon as the 
 temperature rises to summer heat, there is a great di- 
 vergence between the coarse amalgam and the fluid 
 quicksilver, and, as a result, the upper part of the plates 
 becomes incomprehensibly hard and dry, in spite of an 
 increase in the quantity added, while the more lively 
 and thinned quicksilver runs rapidly off the plates, is 
 floured and lost, carrying with it the increased quantity 
 of gold it is now capable of dissolving, lost forever. 
 As a result, there is a poor efficiency of work that the 
 amalgamator cannot explain even to himself. 
 
 In pan-amalgamation of silver ores, the pulp is heated 
 to the boiling point of water, either by live steam, or a 
 false bottom, and all have acknowledged this to be es- 
 sential even on pure chloride ores, not only on account 
 of the chemical action, but also to put the quicksilver 
 in its most efficient condition. In the cheaper gold 
 amalgamating this can not be done, economically, owing 
 to the steady influx of cold water through the batteries, 
 but common sense will show the benefit of having the 
 battery water as warm as consistent with expense and 
 the health of the employes. In summer, for all prac- 
 tical purposes, the ditch or spring water becomes suffi- 
 ciently warm in passing through the water-tank and 
 pipes, not to interfere with the efficiency of the quick- 
 silver. But in winter, except in the tropics, the water 
 comes from melting snow, and it is very little above freez- 
 ing, and unless remedied, it is better to hang up tin 
 
HINTS ON AMALGAMATION. 
 
 57 
 
 mill during the cold weather. In some places it is very 
 dangerous to do this, not only on account of the burst- 
 ing of pipes, but when once frozen up it will be difficult 
 to start again before warm weather arrives. It is im- 
 perative then, to keep the mill moving and thorough 
 preparations should be completed during the early fall, 
 
 TANK 
 
 /O STAMPS 
 
 Modern Machinery. 
 
 FIG. 18. 
 
 to provide against a cold snap, even if of rare occur- 
 rence. If the mill is run by steam, this is very easily 
 attended to, but wherever possible, mill-power is now 
 derived either directly from water under pressure, or 
 indirectly from water at a distance, driving an electric 
 plant. 
 
 If steam is employed, the waste steam is conducted 
 through the water tank, never into it on account of the 
 
58 HINTS ON AMALGAMATION. 
 
 grease. This is generally sufficient, but in an excep- 
 tionally cold locality, rather than add fresh live steam 
 directly to the tank, we advise the following arrange- 
 ment: Before carrying the water to the battery, pass 
 it through a coil of pipe placed around the steam-drum 
 of the boiler where it will be amply \varmed by the 
 waste heat emanating from the surface of the drum. 
 As this will make the water uncomfortably warm in 
 summer, have two sets of pipes, one to go direct to the 
 batteries from the tank, and the other for winter use, 
 leading to the coil. The water leaves the tank in one 
 pipe, but within a couple of feet this pipe enters a "T." 
 With short nipples from the other two outlets and 
 globe valves on each nipple, the water can be diverted 
 either way desired. These separate pipes are jointed 
 together again just before the battery pipe is reached 
 by another "T," the water being under control by two 
 globe valves arranged as in the first instance. Figure 
 18 will partially explain the plan. 
 
 In a mill where the power is either water or elec- 
 tricity, the building is made tight by battening all the 
 cracks, keeping the doors shut, and having all the panes 
 of glass in the windows. Have a large wood stove, at 
 least three feet long, and have plenty of wood, not only 
 for the comfort of the employes, who will attend to 
 their work better, but also for the benefit of the amal- 
 gamation. In a cold country it is necessary to have a 
 small boiler solely to generate steam to heat the water 
 in the tank. 
 
 In some localities where water is scarce or requires 
 pumping to elevate it above the mill, the water that 
 conies from the mine is used in the battery. This 
 does not require heating unless the reserve tank is very 
 large and the weather very cold. In most mines the 
 
HINTS ON AMALGAMATION. 59 
 
 drainage "water will not hurt the amalgamation, but the 
 acid in solution from the decomposition of the sul- 
 phides, and the mud and slimes, are a source of vexa- 
 tious delays and consequent expense. The acid eats the 
 screens and they break very quickly, and the slimes 
 choke the pipes and soon fill the receiving tank, unless 
 it is very large. Therefore, it is better, if possible, to 
 use spring and surface water in preference to that 
 pumped from the mine, the only advantage of the latter 
 being its uniform temperature the year round. 
 
CHAPTER III. 
 CLEANING UP. 
 
 As the amalgam accumulates in battery and on the 
 plates, a certain time in each month must be taken 
 to remove it all, not only to get the money locked up, 
 but to do the necessary repairing to the mill for a 
 coming run. It is far better to appoint a regular 
 day and adhere to it as near as possible, as the cleaning 
 up when the owner happens to be at the mine, or the 
 superintendent feels like it, always comes when new 
 shoes and dies are not required, and often when the 
 ore is just in the best condition for profitable work 
 in that month. According to the size of the 
 mill and the richness of the ore, this day should be 
 set aside either once or twice a month. Of course, in 
 certain localities it is not advisable, for obvious reasons, 
 to have exactly the same day in each month, and it 
 cannot be too strongly impressed on those in power, 
 to keep the exact day to themselves until the morning 
 that has been set, when instructions are given to the 
 millmen to hang up, and the night shift to work over- 
 time, in the effort to finish the actual cleaning and re- 
 pairing and start the mill as soon as possible. If the 
 mining property is isolated, with little communication 
 with the outside world, a regular day, once or twice a 
 month, does no harm; but in a community where there 
 are numerous persons unconnected in any way with this 
 particular property, and a section subject to a constant 
 influx and outflow of persons, whether tramps or people 
 
HINTS ON AMALGAMATION. 61 
 
 on special business, it is on the safe side to keep the date 
 secret when the long accumulations are reduced to a 
 portable shape. 
 
 For this reason we have advised the preliminary 
 preparations of a goodly stock of scrapers, sharply-cut 
 rubbers, and the making of the wooden wedges for the 
 shoes, to be always on hand and ready at a moment's 
 notice, so that no estimate of the special day can be 
 made from observing the preliminary preparations. 
 
 In all mines we find rich ore, medium grade, and poor 
 ore, and an efficient superintendent will try to work 
 all these together in the proper proportions to insure 
 dividends, and yet leave no ore carrying value in the 
 mine. A "tenderfoot" owner will be highly pleased with 
 large profits as long as they last, but is always unwilling 
 to part with some of this profit for future development, 
 when the mine has been robbed of its richest ore. 
 Therefore, it is advisable, in the beginning of a run, 
 to work up for some time the poorer ore of the mine, 
 bringing the product up to a regular amount by extract- 
 ing more or less of the richest ore as required. Now 
 it depends not only on the size of the mill, but also on 
 the value of the ore, whether the mill is stopped for 
 clean-up once or twice a month. Should all the ore be 
 low grade, we cannot afford to lose any more time than 
 we can possibly help, and should only take one day in 
 each month, as our dies and shoes can be arranged to 
 last that time without renewal. Even if we remove 
 them before their usefulness has ended we make more 
 money owing to the increased production. In a custom 
 mill, after each lot of ore is worked, of course a thorough 
 and general clean-up must be made, as gold ores are 
 not safe to buy outright, with the limited means of ac- 
 curate sampling which is generally at our service in 
 countries remote from smelters. 
 
62 HINTS ON AMALGAMATION. 
 
 In a mill running steadily on ore from one mine, we 
 can afford to allow a little of the value to remain un- 
 taken at each clean-up, as it will have an average result 
 in six months or a year, and in reality give more money 
 from a greater production. Most superintendents, on 
 clean-up day, remove all the dies from all the batteries, 
 to get the amalgam in the sand and ore which is packed 
 around them, from two weeks' work, and then replace 
 these partly worn dies for another run. We consider 
 this to be a great loss in a year's run, and a case of 
 greatly mistaken economy for several reasons. 
 
 When we first put in the new dies, they were very 
 heavy, and so kept their position, and the tops were 
 absolutely true. Before there was a chance of changing 
 position they became cemented with the rock and sand 
 so as to become an integral part of the mortar. Though 
 the stamps turn at each revolution of the cam shaft, 
 both the shoe and die wear unevenly, but each shoe 
 after a few days will form the greatest crushing surface 
 with its own particular die, in its original position, which 
 has become as fixed as if it were welded to the mortar. 
 This situation will continue till either the shoe or die 
 break from the thinness attained through the steady 
 wearing away of the iron. In addition to this, the 
 quantity of amalgam which settles through this cement 
 will not be of sufficient amount in any one battery, to 
 diminish the total output to such an extent as to be 
 of special moment to secure at that particular time, 
 while in a year's work it will return a much better aver- 
 age. Now suppose partially worn dies are removed, the 
 gravel extracted and the mortar prepared for their re- 
 placing. The tops of the dies are now uneven, perhaps 
 worn more on one side than the other, or cupped, but 
 the shoe corresponding to each die is worn the same, 
 
HINTS ON AMALGAMATION. 63 
 
 and to replace the dies exactly in the same relative po- 
 sition is well nigh' impossible, even with the greatest 
 care, and a useless waste of time as well. The result 
 is, that a point or edge of a shoe strikes on a point or 
 edge of a die, offering a minimum of crushing surface 
 for several days, and using up unnecessarily a great 
 deal of iron, with no benefit per ton of ore worked. 
 The lessened weight of the die also allows it to jump 
 from the blow of the stamp, before the gravel has be- 
 come cemented, and we are specially liable to a cracked 
 die, or, at any rate, one tilted at an angle to its base. 
 After a couple of months at the longest, we find some of 
 the batteries with worn out dies, while others will con- 
 tinue till our next clean-up day. We replace those 
 worn out, and leave the others, after digging out most 
 of the cemented gravel around them, and we get ready 
 for a fresh start in the shortest possible time, and are 
 again making money. We certainly earn no additional 
 money on clean-up day; we only collect that which we 
 have previously earned. 
 
 The previous day to that one agreed on, we examine 
 all the shoes and mark those batteries where we have 
 to re-shoe and put in new dies, while other shoes which 
 are too far worn to last a whole run are also marked 
 for removal, and partially worn ones which have ac- 
 cumulated are prepared for these stamps. A close ex- 
 amination is also made of every part of the mill, includ- 
 ing the engine, if run by steam, and whether the boilers 
 require cleaning. In the case of steam power, the order 
 to clean up is given the night before, as the mill must 
 be stopped at 4 a. m. to allow the boilers to cool suffi- 
 ciently to be blown off. A regular system must be 
 drilled into the minds of the employees, so that each one 
 knows exactly what he is expected to do. The firemen 
 
64 HINTS ON AMALGAMATION. 
 
 attend to the boilers; the engineer cleans and repairs 
 the engine, taking up all lost motion, and then looks 
 over all the line shafts and pulleys, tightening up the 
 bolts on wooden pulleys, relaces or rivets those belts 
 that require it, and does all the other mechanical re- 
 pairing, assisted by the night engineer. The concen- 
 trator men thoroughly clean the machines; go over the 
 plane of the table with straight edge and level, replace 
 all worn out castings, lace the driving belts, and get 
 everything in apple-pie order. The man who attends to 
 the rock-breaker cleans it of all grease and replaces 
 worn out shoes and dies, assisted in this or any babbit- 
 ing by the engineer. The battery men and all others 
 connected with the mill, who have no special duty, are 
 under the direct supervision of the foreman, and help 
 him, first in removing the amalgam plates to the clean- 
 up room, and then to extract the sand from the batteries, 
 clean off all the amalgam from the aprons and get the 
 batteries in general, ready for as speedy a return to 
 starting as possible, and it is with their work that spe- 
 cial instructions must be given. 
 
 Orders are given to stop the mill at a certain time, 
 and a few minutes before, the feeders are shut off, and 
 boards put over the throats of the mortars to prevent 
 any more rock being jarred into the batteries. When 
 the stamps begin to strike iron, two methods can be 
 pursued, either hang up all the stamps or reduce the 
 speed of the mill down to about thirty-five drops per 
 minute, and allow the stamps to drop till the water 
 comes through the screens clear, though still carrying 
 some sand. We prefer this last method for several 
 reasons: we have less gravel to handle, the chuck-blocks 
 and all parts of the mortar are clean, and therefore 
 visible, and any quicksilver or amalgam which is in the 
 
HINTS ON AMALGAMATION. 65 
 
 rock on top of the dies has been thrown out or settled 
 below the tops. The method advocated by some, to 
 hang up all but one battery, and feed this surface rock 
 through it, not only takes a longer time, but requires 
 the workmen to expose themselves to a possible but not 
 probable accident, by working under the stamps with 
 the cam shaft in motion, and they do the work in con- 
 sequence carelessly, and take a much longer time. 
 
 As soon as the stamps are hung up the water is turned 
 off, and preparations at once started to clean up the 
 mill. 
 
 First, the splash plates are washed and laid across the 
 lower apron plate. Second, the screens are removed, 
 washed over the plate and carried to the clean-up room. 
 Third, the lower keys are driven out and the chuck- 
 blocks carefully removed and washed over the plates 
 and carried to the clean-up room. Fourth, the lip plate 
 is washed on both sides and placed on the lower apron. 
 
 The mill crew is now divided. One man is put in the 
 clean-up room and chisels off the amalgam from the 
 chuck-blocks directly into the tray. A second moves 
 the upper halves of the apron plates down over the 
 lower halves, after thoroughly washing down all the 
 gravel and dirt to the trap. He then scrapes the amal- 
 gam from lip plate and splash plate on the upper apron. 
 These two are the day and night shift amalgamators. 
 The others of the crew remove the top gravel from the 
 mortars and dump it into the feeder of one battery. 
 When this top gravel is taken out to the top of the 
 dies the balance of the gravel is picked out around the 
 dies, and those dies extracted which require removal. 
 This cemented gravel is dumped into the barrel or placed 
 in a box alongside of the clean-up pan, and the mortar 
 is thoroughly cleaned, all adhering amalgam on shoes, 
 
66 HINTS ON AMALGAMATION. 
 
 sides and lip of mortar being chiseled off. The worn out 
 shoes are driven off the stems, and the worn out wedges 
 put into a box for examination and future burning. 
 The new dies are placed in position, and the new shoes 
 with the circle of wedges placed on top of the dies. 
 The partitions are taken out of the traps, the water re- 
 moved with a sponge and the settlings added to the pulp 
 taken from the battery. The old shoes and dies are 
 washed in a tub, the amalgam roughly chipped off and 
 the sediment added to that in the barrel. 
 
 These men now tighten all the bolts around the bat- 
 tery and clean the stems and cams of every particle of 
 grease, using a table knife, coal oil and old sacks. 
 When this is done, wooden blocks are put on the dies, 
 the exact height the drop of the stamps is required to be. 
 The feed stamp is given a half-inch more drop, and the 
 two end stamps a quarter inch more than the others, 
 viz., No. 2 and No. 4, and these stamps are set by their 
 tappets. 
 
 The amalgamators and foreman have, in the same 
 time, scraped off all the amalgam from the chuck- 
 blocks and all the plates, and it is stored in kettles and 
 pans, ready for the clean-up barrel; in fact, should be 
 dumped into the barrel as fast as collected to get it out 
 of harm's way. The upper apron is put in place, and the 
 lip plate, splash plate and chuck-block for each battery 
 put on the lower apron. The engine or water-wheel is 
 now started slowly and the shoes driven on, and these 
 shoes are now set by the blocks as the others have 
 been. 
 
 All the amalgam and gravel is in the clean-up barrel. 
 Some water and at least 40 pounds of quicksilver are 
 added, though the amount of quicksilver depends on the 
 quantity of amalgam to be cleaned, and sometimes 100 
 
HINTS ON AMALGAMATION. 67 
 
 pounds and even more are required. We will explain 
 the use of the barrel first, and afterwards the method 
 of procedure where a pan is employed. 
 
 The barrel is placed opposite the door to the clean-up 
 room, in a line with the batteries, and is driven by a belt 
 connecting with the rock-breaker line-shaft. Directly 
 under it is placed a water-tight box 12 inches high, 
 and in the center of this box a worn out die, on which 
 to set one of the enameled pails. On the rear side of this 
 box is an overflow sluice, on which is placed a silvered 
 plate three or four feet long. There are two openings 
 in the barrel, one being a manhole, to dump the material 
 to be worked, and the other a screw plug one inch in 
 diameter, through which the material is drawn on 
 completion of the grinding. To accomplish this attrition 
 there are put into the barrel several pieces of old shaft- 
 ing from one to two feet long, round cannon balls and 
 pieces of broken shoes and dies of all sizes, at least a 
 total weight of 800 pounds. The cannon balls alone do 
 not do either rapid or thorough work, but with the ir- 
 regularly shaped and sized broken castings, all the 
 ore is quite rapidly ground to a slime. 
 
 The cap of the manhole is screwed on tightly, the joint 
 being made quicksilver-proof with a rubber gasket. The 
 driving belt is connected with the pulley on the line 
 shaft, and the engine or water-wheel started. The bar- 
 rel should not run very fast, as the centrifugal force 
 exerted on the iron and material will hinder the grind- 
 ing which is done by the rolling of the castings over the 
 pulp. These heavy castings are carried up the side, till 
 their weight overcomes their inertia, when they slide 
 and roll back to the bottom, and a high speed will tend 
 to carry them, if not all the way around, at least so far 
 that they will only drop and not slide over the pulp. 
 
68 HINTS ON AMALGAMATION. 
 
 We consider that Mr. Preston makes a great mistake in 
 his treatise, where he advises a speed of 70 revolutions 
 per minute, as this speed should never be over 15 revo- 
 lutions, and our practice has been to use from 7 to 10, 
 when the pulp is thoroughly ground inside of twelve 
 hours. 
 
 As soon as the barrel is started, the night shift go off 
 duty, and if it is late in the day, the day shift remain 
 on duty till midnight. The day shift now dress all the 
 plates with the dressing mixture, thoroughly amalga- 
 mate the chuck-block, lip, and splash plates with quick- 
 silver, throw some rock into the battery, replace every- 
 thing, including new screens, and start on a fresh run. 
 All the implements used are cleaned and taken to the 
 clean-up room, the floor is cleaned and all the mill put 
 in apple-pie order once more. 
 
 In scraping the chuck-blocks, we take everything down 
 to the clean copper, but great care must be exercised in 
 scraping the silvered plates, not to go into the silver 
 coating at all. This is not so very difficult, but for this 
 reason the work should be done by the amalgamators, 
 or those who are careful in their operations. There 
 is a great difference in the "feel" of the scraper when 
 going through amalgam or into the silver the latter 
 being very much harder and smoother. In fact it very 
 frequently feels like the surface of glass. The scrapers 
 must have perfectly true edges and be very sharp, with 
 an end like a wood chisel. The flat side is put against 
 the plate and a steady pressure exerted, never a chip- 
 ping or striking motion. The barrel is allowed to run 
 till there is a steady swish and no grinding is heard. 
 To be on the safe side, it is better not to open it till 
 the next morning when it is certainly ground most 
 thoroughly. The belt is thrown off and the barrel turned 
 
HINTS ON AMALGAMATION. 
 
 69 
 
 till the manhole is on top. The cap is removed and 
 washed over the manhole, and the enameled pail (placed 
 on top of the die directly under the screw-plug), and the 
 box, are filled with water from a hose, which hose is 
 fastened to and kept in the pail. The screw-plug is 
 removed, and as the amalgam, quicksilver and slimes 
 flow out into the pail, it is constantly stirred with a wooden 
 or iron paddle, so as to keep the contents in constant 
 
 ModernMachinery. 
 
 agitation. Whenever no more will run out by itself, 
 the hose is turned into the barrel, and the pieces of iron 
 taken out, each piece being thoroughly washed. All this 
 time the contents of the pail are kept agitated, so that 
 only the heavy amalgam and iron remain, all the sand 
 flowing into the big box and from there over the waste 
 sluice plate. After all the iron is removed, the inside 
 of the barrel is thoroughly cleaned with a broom and 
 the clear water, and our clean-up is finally collected in 
 
70 HINTS ON AMALGAMATION. 
 
 the pail, but it still requires some work which must now 
 be done by hand. We give a cross section of barrel, pail 
 and box in Fig. 19. 
 
 The pail is carried to the clean-up room and the super- 
 imposed sand and iron panned in small quantities at a 
 time. The sand is washed away and the iron picked 
 out by hand and extracted with the magnet, until 
 nothing but the quicksilver and amalgam is left. This 
 is squeezed into balls of convenient size, and, with that 
 collected each day, is now ready for retorting. In some ex- 
 ceptionally unsafe localities it might not be advisable 
 to delay the retorting till the day after the clean-up, and 
 in that case all the dirty amalgam is kept separate from 
 the gravel and sand, and is first cleaned by itself in the 
 barrel. In this case there is only need of putting in the 
 cannon balls. The machine will clean and soften the 
 amalgam in less than an hour, when it can be drawn 
 off as described above, the iron extracted and retorted 
 at once. After this is done, all the sand and gravel is 
 put into the barrel, together with the different sized 
 pieces of iron, and is ground till the next day. The 
 amalgam resulting from this is stored in the strong box 
 till the next clean-up. 
 
 Though the barrel is more generally used in gold mills, 
 some mill men prefer a grinding pan, which is at all 
 times open to inspection, and can be fed with fresh ma- 
 terial without stopping and cleaning out the previous 
 charge. Differing from a silver-amalgamating pan, this 
 one combines the work of both the grinding and amalga- 
 mating pan and the settler. The pan should have iron 
 shoes and dies, and three outlets at different heights, 
 closed by wooden plugs, in addition to the main duct 
 set below the bottom of the die. The overflow outlets 
 conduct the tailings directly over a sluiceplate, while 
 
HINTS ON AMALGAMATION. 71 
 
 the main duct discharges into a water-tight box, fixed 
 with old die and pail. The overflow from this is carried 
 to the same silvered plate that the slimes ran over. This 
 is shown in a cross-section, Fig. 20, which represents 
 only the outlet part of the pan. The speed should be 
 about 30 revolutions per minute, and the modus oper- 
 and! is as follows: The amalgam alone is first ground 
 with the muller down and a sufficient addition of quick- 
 silver to thin it and only a little water. When thor- 
 oughly ground, which should be done in an hour at the 
 longest, water is added, the muller slightly raised, and 
 the overflow plugs opened in succession, with clear 
 water constantly running in till there are no more 
 slimes running out. Then the main duct is opened and 
 the amalgam and quicksilver run into the pail. After 
 all has run out that will, the machine is stopped and the 
 balance swept out with the whisk broom. After the 
 amalgam is cleaned, a charge of the gravel is put in 
 and 40 pounds of quicksilver, and ground moderately, 
 when all that will run down to the lowest overflow plug, 
 after thinning with water, is allowed to escape. The 
 plugs are then put in and it is filled up with more of 
 the gravel. This is continued till all of the scrapings 
 are in the pan. When this is all ground, the main duct 
 is opened at the very last, and the amalgam, quick- 
 silver and iron are run into the pail, and when the iron 
 is separated the amalgam is panned and squeezed. 
 
 The advantages of the barrel over the pan are: First, 
 it takes less power to run. Second, it does not require 
 so much skill to handle. Third, it is a thorough grinder 
 and amalgamator. Fourth, the cost of wear and tear 
 is practically nothing, as worn out castings are used. 
 Fifth, its contents cannot be tampered with, unless the 
 machine is stopped. 
 
72 HINTS ON AMALGAMATION. 
 
 The disadvantages are: First, it can only be run by 
 hearing. Second, only one charge at a time can be run, 
 and not continuously as in a pan. Third, the separation 
 of sand from amalgam has to be done on discharging the 
 contents, when the pulp is thick and capable of carry- 
 ing off values. 
 
 As the advantages considerably more than balance 
 the objections to it, we would advise the employment of 
 a barrel. 
 
CHAPTER IV. 
 RETORTING AND MELTING. 
 
 The kind of a retort we require in our mill-plant, 
 depends entirely on the amount of amalgam we 
 have to distill at each clean-up. There are two 
 varieties in use, the stationary ones, always used in 
 silver mills, but only employed in gold mills when the 
 amount of amalgam runs over 1,500 ounces; and port- 
 able retorts in sizes holding from 30 ounces and up- 
 wards. If the number of stamps exceeds 40, and the 
 ore is of good grade, we will require a stationary re- 
 tort, but its use is of much less importance in general 
 mill work than tbe portable ones. 
 
 Where retorting of large quantities is required, we 
 must have a building entirely separate from the mill. 
 This building will contain one room for the retorting 
 and melting furnaces, and one for the assaying and 
 chemical department, with a small room in which the 
 delicate balances, assay accounts and such things which 
 require care, are kept. The retort is p*; A in the center 
 of the room and the outlet from the fire box extends 
 to a chimney placed to one side. Into this chimney, 
 from the other side come the flues from the two melting 
 furnaces and the muffle furnace. All around the fur- 
 naces the floor is covered with iron plates at least four 
 feet wide, the remainder of the flooring being brick 
 set very closely together. The retort is placed hori- 
 zontally and is closed by a cap covering the whole in- 
 terior diameter, while the outlet for the escape of the 
 
 73 
 
74 HINTS ON AMALGAMATION. 
 
 quicksilver, is a small orifice at the top of the rear 
 end, from which it is conducted by a water-jacketed 
 pipe to a receiver, which is an iron tank filled with 
 water. The balls of amalgam are placed loosely in trays 
 which just fit the contour of the bottom of the retort. 
 These trays are first thoroughly coated with chalk to 
 prevent the gold sticking to the iron when softened by 
 the heat. When all the trays are pushed in, the cap 
 is put on and keyed very tightly. Now a tight joint 
 cannot be made with iron against iron, and no gaskets 
 will stand the heat, so we must find a joint unaffected 
 by the heat or the action of the quicksilver. There are 
 several substances at our disposal, and the choice de- 
 pends only on the presence of one or the other and its 
 relative cost. The luting material can be pure clay, 
 either white fire clay or colored, as the heat is not suf- 
 ficiently high to melt or even thoroughly bake it. The 
 most common material employed is sifted woodashes, 
 either mixed with water alone or with the addition 
 of salt. Either material is first screened through the 
 40 mesh sieve, and all lumps in the clay or cinders in 
 the ashes thrown away. A small portion is mixed and 
 puddled with a little water, until it can be moulded in 
 any form without breaking, and yet carries no surplus 
 water. As the puddling is carried on, either water 
 or ashes are added till the right quantity of the proper 
 consistency is obtained. At first a novice is apt to add 
 too much water, the paste seeming to be too dry, but 
 on working it with a knife, it grows softer and more 
 liquid, so that only after considerable puddling and 
 slight additions of ashes is it possible to get it thick 
 and at the same time soft. When ready the cover is 
 laid in a horizontal position and the lute put all around 
 the edge in the recess made for it. It is put on quite 
 
HINTS ON AMALGAMATION. 75 
 
 thick, carefully smoothed with the knife till the sur- 
 face is perfectly homogeneous, when the cover is placed 
 exactly in its place against the retort and tightly keyed. 
 The surplus lute is squeezed out all around the cover. 
 This is scraped off, and the junction between cover 
 and retort smoothed with the knife. 
 
 A small fire of shavings and wood or bark, is now 
 started and the retort gradually warmed, care being 
 used to keep a small fire till all the metal is thoroughly 
 heated. This is to prevent the deflagration of the amal- 
 gam, as well as any danger of cracking the retort itself. 
 The heat is gradually raised till the bottom of the re- 
 tort is a dull red. Then the quicksilver will begin 
 to vaporize. No fuel but wood must be used, and there 
 is no advantage in trying to hurry the distillation. It 
 will take just so long, as there is only a fixed area 
 for its escape in the outlet pipe, and if this is crowded 
 by the pressure of the quicksilver gas in the retort, 
 there is danger of some escaping before the condensa- 
 tion takes place, thus endangering the health of the 
 operator and also of breaking the joint where the con- 
 densing pipe is fastened -to the retort itself. After the 
 quicksilver begins to collect in the tank, the heat is 
 slightly raised and the retort kept at a cherry red till 
 the amount of quicksilver coming from the pipe slack- 
 ens up. The pipe is now gently tapped with a hammer 
 occasionally and the fire kept up till no more quick- 
 silver, not even a drop, can be collected on holding 
 the hand under the pipe and tapping it smartly. When 
 this is found to be the case, the fire is allowed to burn 
 out, or is drawn and the retort left to cool. This takes 
 several hours on account of the mass of metal which has 
 been heated so thoroughly. 
 
 For this reason, we try to start the fire in the after- 
 
76 HINTS ON AMALGAMATION. 
 
 noon, and finish the retorting during the night. As 
 soon as it has become thoroughly heated, it is safe to 
 leave in the care of the watchman as no one is able to 
 open the retort or abstract the metal as long as it re- 
 mains so hot. It is rarely cool enough to open with 
 safety till 7 a. m., the next day, and it should not be 
 touched till the arrival of the one in authority. When 
 ready, the cap is removed and the trays taken out and 
 placed on the iron plates to cool still more. If the re- 
 torting has not been done too rapidly and with too 
 high a heat, hard to get with wood fuel, the gold should 
 still be in its pristine balls, now, however, porous and 
 spongy. In the bottom of each tray we always find 
 some of the gold joined together, being partially melted 
 from its proximity to the red-hot iron; but it can be 
 easily broken with a blow of the hammer into conveni- 
 ent weights to handle for the subsequent melting. 
 
 At most mines, the amount of amalgam at each cle^n- 
 up is small in actual bulk, and can be handled with the 
 portable retorts. Each mill. should have two on hand, 
 of different sizes, the largest according to the rapacity 
 of the mill and the richness of the ore, capable of iiold- 
 ing in one charge the total of the clean-up. A retort 
 must never be filled more than three-quarters of its 
 capacity. The danger from over-loading is not appre- 
 ciated by the average person till a serious accident 
 occurs. Under the influence of the heat the whole mass 
 swells very much, and we have seen, from putting too 
 much amalgam in, first, the complete choking of the 
 outlet pipe by amalgam, and then when the pressure 
 became too great the sudden forcing of several pounds 
 of amalgam with quicksilver vapor, into the receiving 
 tank. In some cases if the retort was old or the cap 
 improperly fastened, a very serious and dangerous acci- 
 
HINTS ON AMALGAMATION. 77 
 
 dent would happen from the explosion of the retort 
 itself. 
 
 The portable retorts are in two shapes, those with 
 a flat cover, and those with a curved cover and known 
 as the Nevada retort. The latter style is very much 
 preferable, as it gives, under all circumstances, A re- 
 serve space for the quicksilver vapor and allows a 
 little more latitude in filling the retort, besides giving 
 a much stronger keyway and general fastening. 
 
 Before putting in the amalgam, every part of the re- 
 tort must be examined. First see that the pipe is tightly 
 screwed into the cover, and is perfectly clear, tapping 
 it with a hammer and blowing through it. With a 
 new one, be sure and, coat it thoroughly, because, if 
 the gold adheres to the iron in any one place, in sub- 
 sequent cooking with every care taken, it is generally 
 attached to the same place. If the retort has been 
 in use, remove all adhering particles of gold with a 
 chisel and coat most thoroughly. We have a choice 
 of two coatings, one, which we consider the best, is of 
 soft chalk, rubbed on dry from the chunk or powdered, 
 mixed into a paste with water, and plastered smoothly 
 all over the inside; the other, a thin paste of sifted 
 wood ashes and water, which is thoroughly daubed all 
 over the interior. If a paste is used, the retort should 
 be dried before putting in the amalgam. The quicksilver 
 condensing pipe should always be water- jacketed, and 
 can be bought already prepared in this way. This jacket 
 consists of an iron or tin pipe two to four inches in 
 diameter, and made water tight at each end, through 
 which the condensing pipe passes. At the lower end, 
 the furthest from the retort, there is put in a part of 
 a hose coupling to which the hose conveying the cold 
 water can be screwed. At the upper end Is a small 
 
78 
 
 HINTS ON AMALGAMATION. 
 
 outlet, to which a piece of quarter inch pipe is screwed. 
 This pipe is bent and carried down on top of the con- 
 denser, discharging into the kettle which receives the 
 metallic quicksilver. If not bought with the retort, 
 any tinsmith or capable engineer can make a tin cyl- 
 inder of the required size, solder in a hose coupling at 
 the lower end, and solder the whole tightly to the pipe 
 
 at each end, The constant flow of water will prevent 
 any melting of the solder (See Fig. 21). 
 
 Where a water-jacket is used, the end of the outlet 
 pipe is placed a little below the surface of the water 
 in the receiving kettle, an inch being ample. Sometimes 
 it is necessary to use a retort, having only the naked 
 pipe over which water is poured from a dipper. In this 
 case care must be taken that the orifice of the con- 
 densing pipe is partly out of the water, and this is very 
 rarely looked into by mill men. The danger of a diminu- 
 tion in the heat consists in the creation of a partial 
 vacuum in the retort, which then sucks up water from 
 the kettle if the pipe is wholly immersed. This water 
 is converted into steam and causes an explosion of great 
 
HINTS ON AMALGAMATION. 79 
 
 danger. With part of the orifice out of the water, only 
 air is sucked up, which causes no sudden increase in the 
 internal pressure; but we are confronted with another 
 danger, that of salivation from the escaping quicksilver 
 gas, unless we close the orifice in some way. Now we 
 wish to impress this point very, very strongly on all 
 those intending to retort the amalgam without a water- 
 jacket. Even if they are fortunate, time after time, 
 in having no serious accident, they will always be more 
 or less salivated, and it takes a very slight exposure to 
 quicksilver fumes to find the teeth becoming loose and 
 other evidences of quicksilver poisoning. The way to 
 prevent it is this: The pipe is wrapped with burlaps or 
 gunny sacks, and a V of tin placed underneath, sus- 
 pended by wire, to carry the water poured over the 
 upper part of the pipe, away from the fire. This sack- 
 ing is extended several inches beyond the end of the 
 pipe and into the water of the receiving kettle. In this 
 case the pipe must be straight from the retort to the 
 kettle, with no bend, as shown in the sketch of the 
 water-jacketed pipe. The wet sacking prevents any 
 escape of the quicksilver fumes, and yet part of the 
 orifice of the pipe is out of water. Should a partial 
 vacuum be formed inside the retort, the only effect is 
 to suck the gunny sack against the mouth when the 
 air enters freely through the web. 
 
 The retort has been chalked, all parts examined, and 
 the amalgam in balls ready to be packed in it. This 
 packing depends on the subsequent handling of the re- 
 tort-metal. Where not convenient to melt into a bar at 
 the mine, it is just as well to ship the gold just as it 
 conies from the retort, but in that case we want to have 
 it as compact a mass as possible. If it is melted at 
 once it is better to keep it in its original balls from 
 
80 HINTS ON AMALGAMATION. 
 
 which the quicksilver has been distilled. When the re- 
 tort metal is shipped, the balls are broken and the 
 amalgam packed with the iron pestle into one solid mass, 
 that around the sides particularly being smooth, so as 
 to leave no thin ridges to break away. When it is all 
 smoothed, a hole is bored in the center to the bottom, 
 with an iron rod, to act as a vent for the escaping gases 
 and to prevent the entire mass from being raised by 
 the pressure underneath before it makes its own vent. 
 In this case also the heat during the last of the operation 
 is raised to a bright red so as to anneal and partially melt 
 the gold and so hold it together. When it is melted on 
 the spot, the balls are put in unbroken, and sometimes 
 each ball is wrapped in a piece of cloth or paper. The 
 wrapping is unnecessary and only a false idea of exces- 
 sive carefulness, which results in the distillation along 
 with the quicksilver of pyroligneous acid, and this very 
 quickly chokes the condensing pipe and flours the quick- 
 silver, hindering the operation considerably. 
 
 After all is ready, the lute of wood-ashes, with or 
 without salt, is mixed and put on the cover, not on the 
 retort; the cover is put in place and keyed tightly, and 
 all the oozing luting is scraped off and smoothed around 
 the joint. 
 
 The next question arises, how and where to retort. 
 Retort out of doors, or under an open shed, where there 
 is no danger of tire. Do not use the blacksmith forge, 
 because too much heat is unconsciously given with the 
 bellows, nor a furnace into which the retort is set, as the 
 heat is not under control, while it is hard to remove a 
 heavy and hot retort, and in both these cases no direct 
 heat can be applied to the bottom. Make a tripod with 
 a ring into which the retort just fits, and high enough 
 to allow a good fire place underneath. This can be 
 
HINTS ON AMALGAMATION. 81 
 
 made by any blacksmith, and the only point to be ob- 
 served is that the legs shall be extra thick and strong, 
 to withstand any bending from the heat and weight. 
 In addition to the welding of the legs to the ring, put one 
 or two rivets in each leg, for additional security. Fig. 
 22 shows this tripod. 
 
 The tripod is set within distance of the water pipe and 
 the retort put in place, the hose connected and the re- 
 ceiving kettle, partially filled with water, is put at a 
 slight inclination with the end of the condensing pipe 
 submerged in it an inch. A small fire of shavings and 
 a little oily waste is started directly under the retort. 
 This is gradually increased with either pine bark or 
 wood, but slowly until all the air is driven out, and a 
 little quicksilver begins to run. Then the fire is in- 
 creased and the retort kept at a cherry red till no more 
 quicksilver can be collected, after tapping the pipe. 
 When this is shown to be the case, the fire is withdrawn, 
 the pipe taken out of the kettle, and the cover of the 
 retort taken off. To prove that no more quicksilver is 
 left, take a cold shovel, wet it and hold over the open 
 retort, when it will be covered with a white film if any 
 of the quicksilver remains. Before the retort has a 
 chance to cool, dump out the retort metal into a pan 
 set on an iron plate or directly on the plate, and scrape 
 out any adhering gold. The gold must now be cool 
 enough to handle with the bare hands, before it is 
 weighed, or a correct estimate of its weight is not ob- 
 tained. It should be porous and bright, or the amalgam 
 has not been properly cleaned. 
 
 The question as to what fuel to use is of some moment. 
 Do not use charcoal or coke, even though on account of 
 the greater heat it would be surmised that time can be 
 gained. The top of the retort must be kept as hot as the 
 
82 HINTS ON AMALGAMATION. 
 
 bottom, and this can only be done with a fuel which 
 gives strong flames. The best fuel is pine bark, but if 
 this is not easily available, dry wood, either pine or 
 other soft wood, will do as well. The wood is sawed 
 into two-foot lengths and split to small size. When the 
 fire is well started, some pieces are placed under the 
 retort between the legs of the tripod, and a complete 
 circle of the wood, placed on end, is stacked against 
 the ring of the tripod, which forms a chimney for 
 draught and a gradually increasing heat. Frequently 
 only one firing is necessary when placed in this way. 
 
 The retort metal, if shipped direct, is now wrapped 
 carefully in paper and then sewed and sealed in an 
 ore sack of canvas. If melted on the premises into a 
 bar, we can use the assay furnace, provided there is no 
 special furnace. The fuel used for melting is either 
 charcoal or coke, the latter good English and not gas- 
 house coke. The coke is very much to be preferred. 
 The black-lead crucible, for a long time before use, 
 should be put bottom up on the boiler or other hot place, 
 to get thoroughly dried out. It is then put into the fur- 
 nace where there is a hot fire dying out. Here it is 
 put bottom side upwards, and left to be annealed till 
 everything is cold. It is then ready for the melting of 
 the gold attended by a minimum of danger as regards 
 cracking. Before the retorting is completed a fire is 
 started in the furnace, and the crucible, resting on a 
 piece of brick, is placed in position. The fire is gradually 
 increased till the crucible is heated almost to a white 
 heat, and the supply of incandescent fuel just reaches 
 to the top of the crucible. The retort metal is now put 
 in from an iron scoop. This can be home made from 
 rolling a thin sheet of Russia iron so that it has a smaller 
 diameter at one end, or a scoop that can be purchased 
 
HINTS ON AMALGAMATION. 83 
 
 ready made. The crucible is filled nearly to the top 
 with the retort metal, and a tablespoonful of a mixture, 
 containing ground borax and a little sand or ground 
 glass, is at once added. If all of the metal cannot be 
 added at once, the first charge is thoroughly melted 
 before any more is put in. On each subsequent addition 
 a little more of the fluxing material is used. When all the 
 metal is in quiet fusion, the supernatant slag is skimmed 
 off by means of gently passing a coiled rod of cold iron 
 (Fig. 23) over the surface, frequently chilling the slag 
 by pressing it on an iron plate, or slight immersion in 
 water. When the slag is removed, the graphite pot is 
 lifted from the fire and the contents, after thoroughly 
 stirring and mixing with a paddle made from old crucible 
 and heated in fire before use, are carefully poured into a 
 mold already prepared for them. This mold has been 
 first smoked evenly by inverting over a fire of cotton 
 waste, coal oil and pitch or rosin, and then heated as 
 hot as possible by exposure to the heat from the top 
 of the furnace. As soon as the gold has been poured 
 a pinch of candle scrapings is thrown on top and the 
 mold is covered by an iron plate or a piece of wood and 
 left to chill. When solid, but still red hot, the mold 
 is inverted and the gold brick at once immersed in a 
 cold pickle, consisting of water acidulated with sul- 
 phuric acid. When cold enough to be handled with the 
 bare hands, it is removed and scrubbed with a brush. 
 Any projections are hammered flat, and the bar is ready 
 for chipping and weighing. Even if no assay is made 
 at the mine, always chip off two pieces from diagonally 
 opposite corners, mark them with date and number of 
 bar, and file away, as a precaution against any future 
 dispute. Stamp on bar number and weight in troy 
 ounces; but it is advisable to abstain from putting oij 
 
84 HIN'TS ON AMALGAMATION. 
 
 fineness of bullion or its value. In any and all circum- 
 stances the buyer will have it remelted and assayed, 
 and it is better for the seller not to publish so widely 
 his own knowledge of its value. 
 
 Practically all gold bullion from placers and quartz 
 mines, saved by amalgamation, contains some silver, and 
 this has to be separated before the gold is ready for 
 coining or other purposes. This cannot be done at the 
 mine, and as some gold is lost to the seller in remelting, 
 it is of advantage to ship the bullion as retort metal, 
 save the expense of fuel and the loss in melting. Under 
 any circumstances a fixed charge has to be paid to the 
 refiners. 
 
 Louis Falkenau, State assayer of San Francisco, tells 
 us that if the slag dipped off is powdered and panned 
 and old crucibles treated in the same way, there is no 
 loss in melting. And also, if the bar has been properly 
 melted and mixed, the chips will ensure a control which 
 he considers important. 
 
CHAPTER V. 
 CONCENTRATION. 
 
 In the beginning of this series of articles, a rapid 
 summary was given of all the various processes em- 
 ployed in milling that seemed to be of moment. The 
 most minute details have been explained in connection 
 with the extraction of the free gold. We come now to 
 the consideration of the valuable residues still remaining 
 in the pulp, to which the generic name of sulphurets has 
 been given. As the financial standing of gold mining 
 to-day depends exclusively on the ability to extract all 
 the value in the ore, most careful attention is paid to 
 the concentration of these sulphurets at a small expense 
 from the worthless rock into a paying and portable 
 product. 
 
 Rival states have waged a bitter controversy over this 
 matter of concentration, contending that each one's spe- 
 cial process is the best and should be more largely 
 adopted in other places. We refer to the radical variation 
 in mill practice as pursued in certain localities of Colo- 
 rado and in California. The author is free to confess that 
 he is prejudiced in favor of the California method, as 
 giving a higher percentage ultimately, in all the sections 
 so far investigated. However, the method must be abso- 
 lutely correct and not a partial adaptation. 
 
 In iron and copper pyrites (the commonest gold-bearing 
 minerals) the majority of the gold is still in a metallic 
 state, microscopic leaves in the fractures of the mineral, 
 and if pulverized to sufficient fineness can be caught 
 
 85 
 
86 HINTS ON AMALGAMATION. 
 
 with quicksilver, but the expense is increased in a pro- 
 hibitive ratio, owing largely to the small duty performed 
 by each stamp per horse-power consumed. Again, the 
 sulphurets have been so depleted of their values that it 
 is only possible and advisable to save them where they 
 have more value than the gold they still contain, and 
 where the cost of concentration can be done without 
 additional expense beyond the first outlay in plant. The 
 first condition is obtained by the demand of lead and 
 copper smelters for an iron flux, and their nearness to 
 the mines. This, and this only, has brought the Gilpin 
 county method into a prominence which it does not war- 
 rant. Remove the smelters from Denver, and it will be found 
 to be economically impracticable to save the concen- 
 trates of that district after the method of milling em- 
 ployed. We are not trying to convert the millmen of that 
 district to our way, but the majority of gold mills have 
 not the good fortune to be in such close proximity to 
 smelters, and it is suicidal to pursue such a method any- 
 where unless as propitiously situated. The Black Hawk 
 mills save an average of 80 per cent., according to trust- 
 worthy sources, and, we honestly believe, this percentage 
 can be raised to over 90 per cent, and at a less expense 
 per ton, if they will stop trying to corrall every speck 
 of the free gold inside the mortar. We wish to be very 
 minute, so that the other districts of the world can judge 
 in regard to the feasibility of the process. 
 
 We have mines in this state, in which the ore is very 
 simflar to that of Gilpin county, the value all in the 
 sulphurets, which are working over 90 per cent, of the 
 assay value, and at a less cost per ton. Of these the 
 most notable is the "Golden Gate," of Tuolumne county. 
 We would advise any person who is considering the rela- 
 tive merits of the two processes, to make some inquiries 
 
HINTS ON AMALGAMATION. 87 
 
 first, not from the manufacturers of the machinery, but 
 from the owners or superintendents of some of the sul- 
 phuret mines in this State. It is not a question of slow 
 or fast drop, but of high or low discharge, and the fine- 
 ness of the mesh of the screen. 
 
 We are all trying to save as much of the value in the 
 mill as possible and at a minimum of expense, and to 
 do this we have to harmonize the two distinct processes 
 of amalgamating and concentrating, and not unduly 
 favor one at the expense of the other. 
 
 Now gold has a very high specific gravity and yet be- 
 comes so fine that it floats. It is also malleable, but 
 not often brittle, and, therefore, is comminuted very little 
 after being freed from its enclosing gangue. Sulphurets, 
 on the other hand, have much less specific gravity, 
 and are always brittle, which brittleness increases di- 
 rectly as their richness in the precious metals. Expose 
 fine sulphurets for an instant only to the air and they 
 will float on the surface of the water for miles or till 
 submerged by the water falling an inch or more. 
 
 Go at any time below any of the mills of the Black 
 Hawk district, except immediately after a heavy storm, 
 and the banks of the gulch will be found lined with sul- 
 phurets, while in the eddies, all the detritus is composed 
 of pure concentrates. Go below a California mill, prop- 
 erly handled, and only traces are found on panning, and 
 none is seen with the naked eye. The assay of the tail- 
 ings for each ton in Gilpin county may be low, but the 
 aggregate in a year that can be saved, is so large that it 
 seems almost criminal to allow such a loss to exist. The 
 keynote of this loss is owing to the unnecessary sliming 
 of these very brittle sulphurets. First, the 14 inches 
 or more that the pulp has to rise through, before dis- 
 charging, keeps all the ore to be struck so many times 
 
88 HINTS ON AMALGAMATION. 
 
 by the stamps that the sulphurets are ground to a slime 
 and this is secondarily aided by the fineness of the 
 screen openings, but only partially, as we have very fre- 
 quently had to employ a No. 12 punched-slot screen on 
 California ores, to save all the values. The output of 
 this is as fine as that of a 50-mesh wire screen. 
 Now, the greatest trouble to be found in concentration, 
 is to save the slimed mineral, and often the slimes are 
 removed with a point box and settled separately in order 
 to make any showing at all satisfactory. It is, there- 
 fore, obligatory to crush as coarsely as is consistent with 
 the loss in the tailings, which loss must be located, 
 whether in the sand or slimes. If in the sand, finer 
 crushing is required till we are satisfied we have reached 
 the most practical, that is, economical efficiency. Of 
 course, it is advisable to save all free gold possible with 
 the quicksilver, but not to such an extent as to ruin the 
 concentration of the remaining values. No matter how 
 fine the sulphurets are pulverized, they will still contain 
 free gold, and even after roasting this free metal will 
 not be absorbed by quicksilver; but it is only with a 
 chemical agent that the gold is saved. If impartially 
 considered, all will agree that the object of stamping 
 is to save all possible value in the mill, and the observa- 
 tion that can be made by any one below the mills em- 
 ploying the different methods, should practically prove 
 the advantage of the process employed in this state. 
 
 As there are tricks in all trades, there are certain points 
 in regard to the handling of concentrators and their pro- 
 duct which will materially add to the efficiency of the 
 work performed. With some styles of machines, a great 
 advantage is gained by sizing the material to be treated 
 with the aid of "spitzlutten" or ascending columns of 
 water under varying pressure, but this is not necessary 
 
HINTS ON AMALGAMATION. 89 
 
 with a shaking table working without a jar. In fact, 
 unless there is an undue proportion of clay slimes, the 
 side-shake, endless-belt, machine will do its best work 
 on ore just as it leaves the battery screens, and sulphurets 
 will be separated by the machine which require great 
 care and ingenuity to save after its deposition in the 
 concentration tank. 
 
 A vanner in perfect working order should show the fol- 
 lowing state of affairs: First, no jar whatever, on plac- 
 ing the hand on any part of the upper frame; second, a 
 thickness of pulp on the bed below the ore-spreader of y 2 
 inch, slowly flowing towards the foot of the machine, 
 with a smooth surface and no ripples, and this current 
 must not be faster on one side of the machine; third, a 
 sand edging on each side, along the flange of the belt, 
 of equal width and not to exceed 2 inches; fourth, at 
 the foot of the machine, the taiilngs to escape towards 
 the middle of the belt, leaving the flanges and a small tri- 
 angular section of the belt free from sand and exposing 
 clear rubber; fifth, the sand to be kept in view up to 
 the rear side of the clear water box, but showing no dry 
 fingers; sixth, the sulphurets to be passing over the head 
 of the machine in bands between the clear water jets and 
 showing absolutely no sand or slimes; seventh, when the 
 belt leaves the concentration tank, that it shall be cleaned 
 of all the sulphurets; eigthth, that the concentrates de- 
 posited in the box and saved by the machine shall be also 
 saved by the operator^ and not allowed to escape in the 
 overflow waterTl < ~i."\ 
 
 First, no jar. In setting up the machine, the posts and 
 sills are mortised and placed in position, with the keys* 
 driven in on the outside of each post. Then the shoul- 
 ders on each post are cut to scant width and full depth; 
 that is, for a 4 foot machine the measurement between 
 
90 HINTS ON AMALGAMATION. 
 
 posts calls for 5 feet 6y 2 inches, but the shoulders are cut 
 to give a distance of 5 feet 6% inches, and when the 
 lower frame of the machine is put together the bolts 
 are driven in with a sledge, almost cementing frame and 
 posts. If through shrinkage, later on, the machine gets 
 loose, iron or hard wood wedges must be driven in to 
 form a tight joint. The two rollers underneath the 
 machine must have no lost motion, and must not strike 
 the sides of the lower frame. The lost motion is taken up 
 by tightening the two cross tie rods equally. The pre- 
 vention of striking is accomplished by moving the roller 
 either way till it clears each side. This is done by loosen- 
 ing the nut of the rod, on the side the roller should go, 
 and tightening the nut on the opposite side (the one which 
 is striking). See that the flat springs, on which the 
 shaking table rests, do not strike the lower frame, and 
 where one does, drive in the lower spring support. Take 
 up all lost motion of the end rollers, by the gudgeon caps, 
 and see that there is none also in the journals and 
 brasses of the shaft, nor in the spur wheel and spring 
 crank shaft. Last, but most frequently overlooked, ex- 
 amine each one of the little rollers over which the belt 
 travels, and move the chairs till there is no side motion, 
 but that they will still turn easily, and then fasten each 
 chair by driving a wire nail or two into the upper rail, 
 in front of the chair. 
 
 Second, haye a proper bed of pulp. Put a straight edge 
 across top of lower frame and with spirit level make it 
 practically level across, and then place machine on dead 
 center. Take a piece of wood just two inches long and 
 place between upper rail and top of each cross piece of 
 lower frame, and raise or depress lower supports by the 
 bolts passing through lower frame, till this wood just 
 passes easily under lower rail everywhere. The small 
 
HINTS ON AMALGAMATION. 91 
 
 roller next to the main head-roller is raised by a piece 
 of wood a half inch above the plane of the table, but all 
 the other rollers, including the foot main roller, must 
 form a perfect plane. To determine this, a string or 
 straight-edge is placed over the second small roller from 
 the head, and carried over the main foot-roller. Bach 
 little roller is made to touch this, being raised by having 
 a piece of cardboard put under the chair, or lowered, by 
 cutting out a slight shaving from the rail. Discretion 
 must be employed to change only those chairs that 
 affect the entire table. Place the main driving shaft 
 by the three movable boxes, so that the distance be- 
 tween outside edge of lower frame and inside edge of 
 shaft is exactly 2 inches % and 1-32. The machine is 
 now ready to start. The speed of the side-shake is 
 first tried at 190 revolutions per minute, and the lower 
 ends of the machine equally lowered till the grade is 
 about }4 inch per foot, while the uphill travel is started 
 with the small leather belt an inch from the small end of 
 the cone pulley. 
 
 The pulp is now turned on and allowed to run for 15 
 minutes, without altering the machine or until it gets 
 its load. If too light, the foot is raised equally on both 
 sides, but generally it has to be lowered, from being too 
 flat. The water is fixed at a minimum, and the sand 
 is brought up to the water box by increasing the uphill 
 travel. Each machine acts a little differently, so each 
 one is separately regulated, till proper grade and uphill 
 travel are attained. This should be all that is required 
 to put the belt in perfect shape. However, at times, we 
 find a wide expanse of dry sand on one side, and a 
 correspondingly swift current on the other, which must 
 be at once remedied. Knowing that everything is in 
 perfect order, this is at first incomprehensible, until 
 
92 HINTS ON AMALGAMATION. 
 
 it is observed that the strain is^stronger on one throw 
 of the crank-shaft than on the other and the sand is 
 sensitive to the slightest variation. To overcome this, 
 we have two remedies, the first and simplest to remove 
 and bend the spiral drive-spring, at the head of the 
 machine, inclining the point the way the sand is wanted 
 to travel. The second is, to move the entire main 
 shaft, 1-32 to 1-16 inch, in or out, as the case requires; 
 out, if the heavy sand corner is on the same side as the 
 shaft, and in if the reverse is the case. 
 
 Seventh. In order to be sure that the belt is cleaned of 
 sulphurets after leaving the main tank underneath the 
 machine, two series of jets are directed against it above 
 and below, and the pipes must be frequently watched 
 to see that the holes do not clog, most particularly dur- 
 ing the time when the accumulated deposits are with- 
 drawn, and the water rapidly lowered in the tank till 
 it may not submerge the belt. It is also very necessary 
 to observe when we lower or raise the machine, that the 
 belt is not either raised completely out of the wash 
 water, or sunk so deep as to cause undue agitation. 
 When raised out of the water, the conclusion is obvious. 
 If sunk too deep, the belt and flange throw the water 
 back and forth so violently that it slops over the sides 
 of the box, carrying sulphurets as well as making 
 everything sloppy; but the chief fault lies in the fact 
 that the concentrations do not settle here but are carried 
 away with the overflow water. With the least agitation 
 too much escapes in this way. This overflow contains 
 the richest in value as well as the finest in size of all 
 which is saved by the machine, and this brings us to 
 the consideration of the very important subdivision No. 
 8, namely, for the operator to collect that which the ma- 
 chine has saved. It is important, but frequently over- 
 
HINTS ON AMALGAMATION. 93 
 
 looked. The mill is doing good work, according to the 
 assay of the final tailings, but the product does not 
 tally with these assays, owing to lack of care of the 
 concentrates after the machine has extracted them from 
 the pulp. Some minerals, notably nagyagite and black 
 telluride, largely saved by the machine, will float as a 
 scum on the water of the tank, and run away with the 
 overflow unless it is forced under the water, and the 
 same is true in a lesser degree, of all the sulphurets. 
 To overcome this, we always place a piece of rubber 
 belting in a semi-circle, around the inside of the over- 
 flow orifice, which extends at least two inches below the 
 surface of the water in the tank. This requires all 
 the material to be thrust under the water before it can 
 escape; but that which does escape should flow through 
 a very long series of dead-water boxes, in which are 
 placed numerous obstructions to the flow. One obstruc- 
 tion is to place cross-pieces at intervals which extend 
 nearly to the bottom of the box; while another obstruc- 
 tion is to frequently transfer the current through a sur- 
 face orifice to another box in which the current runs 
 in the opposite direction, and the two together are very 
 efficient. A peculiar slime box was lately brought to our 
 observation, in conjunction with a patented slime con- 
 centrator, which appears to be of exceptional value, 
 as presenting great obstruction to the flow of the solid 
 material in the water. We append a sketch of this as 
 of interest, only remarking that the wings are remova- 
 ble. (Fig. 24.) 
 
 These devices prevent as much loss as possible in the 
 slimed material while the machine is running, but there 
 are other losses to be guarded against as well. Each 
 machine has constantly on its bed a greater weight of 
 sulphurets than is commonly supposed, which remains 
 
HINTS ON AMALGAMATION. 
 
 uniform as long as the pulp flows on it and it is kept in 
 agitation. Stop the machine and pulp and allow the 
 water to run and this accumulated load is rapidly 
 washed into the tail-race, a total loss, unaccounted for 
 by the assays of the tailings, and it is a very great loss 
 as well. So that on stopping the machine temporarily, 
 always turn off the water and when stopping for some 
 time, as during clean-up, always work off the load on 
 
 *"/ 
 
 *~E 
 
 ; Eleva.it on !! 
 
 tt _ii 
 
 
 Modern Machinery . 
 
 the belt before stopping the machine. A third source 
 of loss is the careless removal of the concentrates. Twice 
 a day the accumulations are hoed out into a drain box, 
 placed in front of each machine, and the surplus water, 
 after settling by blows or stirring, thrown back into the 
 concentration box. Be sure that the wheel-barrow or 
 car is water-tight, and do not fill it more than three 
 fourths full, as in moving it becomes almost a liquid, 
 from the water held in suspension. Have a separate 
 room for storage which is tight, and save all spillings 
 from shoveling, etc., as they count in a year's time. 
 
 In spite of the most careful settling, the concentrates 
 will carry at least 10 per cent, of moisture, which should 
 
HINTS ON AMALGAMATION. 95 
 
 be eliminated as a matter of economy if for no other 
 reason. If the sulphurets are chlorinated on the ground, 
 this excess of water increases the consumption of fuel 
 in roasting. Generally, however, the concentrates of 
 one mine are too limited in quantity to warrant the erec- 
 tion of a reduction plant, and therefore, they are period- 
 ically shipped to smelter or other custom reduction 
 works. This shipment requires long wagon hauls, be- 
 sides railroad transportation, for which the expense 
 charges are always based on gross weight. It is easy 
 to see the loss in cash returns on the ore when at least 
 one-tenth, and often one-fifth, of the gross weight is 
 barren water, which can be removed at the mill before 
 shipment with only a little trouble and at a very small 
 expense. If dried as soon as removed from the machine, 
 the sulphurets do not oxidize, clinker and cement to- 
 gether, but allow such a thorough mixing at all times 
 as to get accurate sampling and assays. 
 
 The sun is, of course, the cheapest drier, but its use 
 is of doubtful value, if the concentrates are dried on a 
 platform in the open air, as the wind will very quickly 
 scatter several per centum, as soon as they become dry. 
 To use sun heat, a room must be constructed, with the 
 three sides consisting of panes of glass and ventilator* 
 in the roof. In other words, have a conservatory with- 
 out the glass roof. This room need not be very large, 
 as the concentrates, as soon as dried,' are shoveled into 
 a storage bin, where they are sacked, sampled, weighed 
 and shipped. For a 20-stamp mill, make the floor 20 
 feet by 30 feet, putting the room, if possible, on the 
 sunny side of the concentrator room, and place the bin 
 at a lower elevation than this floor. 
 
 For artificial drying, very little heat is required, and it 
 can be procured from waste steam, or any scraps of 
 
96 HINTS ON AMALGAMATION. 
 
 wood chips, etc., that are handy. The top of the drier is 
 made of sheet iron with raised sides. When the sulphur- 
 ets are nearly dry, they will run like quicksilver on 
 being touched or stirred. In using steam, a coil of pipe 
 is placed underneath the plate, which comes from the 
 engine and which discharges the condensed water and 
 steam outside the building. In using fire direct, it is 
 necessary to build a regular drying furnace, with a rela- 
 tively large fire-box. The simplest form is to place the 
 iron tray directly on the fire-box, and create the 
 draught with a short piece of pipe at the further end. 
 However, as in all cases it is better to do well anything 
 that is undertaken, we would advise the erection of a 
 regular drying furnace. This will consist of a fire-box 
 and bridge at one end of the plate and a shallow space 
 under the plate from the bridge to the flue, all to be 
 built of red brick and fire clay. 
 
 As soon as the sulphurets are dry, they are shoveled 
 into a storage bin, till wanted for shipping. In sacking 
 them the closest woven canvas should be used, and 
 before each sack is sewed a sample is taken with a fryer 
 such as used to sample butter, or made by splitting 
 a half-inch gas pipe. Another satisfactory method is 
 to use a quarter-inch auger. Do not expect any check 
 on the value when a pinch is taken from the top of each 
 sack, as a sample must extend clear to the bottom. 
 
 As stated above, the slimes taken from the overflow 
 settling boxes are invariably very much richer than 
 the coarser concentrates which are collected each day, 
 but they are generally very limited in quantity. On 
 account of the small amount, these boxes are only 
 cleaned occasionally, once a month or less frequently. 
 When these are dried by themselves, it is imperative 
 that they shall be uniformly scattered over and mixed 
 
HINTS ON AMALGAMATION. 97 
 
 with the accumulations already in the storage bin, or 
 the mine is never credited with its full value. If sacked 
 by themselves, the one or two samples taken of them 
 and mixed with the 100 or more samples from the 
 vaster amount of the coarser accumulations, will not be 
 nearly as accurate in giving the average value as if 
 all had been thoroughly mixed in the first place, and 
 the 100 or more samples should each contain their proper 
 proportion of these rich slimes. If the space at the mill 
 will allow it, we would advise sampling as done by 'the 
 smelters. The concentrates are shoveled into sacks, but 
 every third, fifth or tenth shovelful is put into a separate 
 pile till all the concentrates are sampled. If the result- 
 ing pile is still bulky, every other shovel is put into 
 the sacks, and then the remainder is shoveled into a 
 cone, spread out, and quartered down till the assay 
 weight is obtained. With the necessary appliances this 
 can be done very quickly. Beside a broom and square- 
 pointed shovel, there are required a sack-filler, and iron 
 cross for both of which ideas we are indebted to a well 
 known smelter near San Francisco. The sack-filler has 
 been copied from that in use on potato ranches, and is 
 an iron cylinder with a funnel top, which is inserted 
 into each sack. (Fig. 25.) 
 
 The iron cross is made of two pieces of iron at right 
 angles, and two sizes should be kept on hand, both in 
 height and circumference. With this cross, each shovel- 
 ful is dumped directly over the center of the cross, and 
 on smoothing the resulting cone, the quartering divis- 
 ions are already accurately determined, of uniform size 
 and position. (Fig. 26.) 
 
CHAPTER VI. 
 
 SAMPLING. 
 
 It is of very rare occurrence to find an assay office 
 attached to a gold mill, but if any intelligent work 
 is done, it is imperative to have absolute technical 
 accuracy at frequent intervals, and not trust entirely 
 to the eye, which is deceptive, no matter how finely 
 trained. In silver mills and other reduction works a 
 qualified assayer who also possesses an insight of the 
 methods in metalliferous chemistry, is absolutely essen- 
 tial to the success of the enterprise. Such wide techni- 
 cal knowledge is not demanded in gold-mill practice, 
 though, of course, of appreciable benefit; but, the su- 
 perintendent or one of the employes of a company 
 must be able to make an accurate determination by 
 fire of the values in the ore and tailings when required. 
 
 Gold is worth $20.67 per ounce, and occurs very irreg- 
 ularly disseminated in the accompanying gangue, when 
 in a free state. On account of its value, a small particle 
 in that piece assayed, might enhance the estimated value 
 of the body of ore under investigation much beyond 
 the working value afterwards determined in practice, and 
 the opposite results might also erroneously be obtained. 
 For this reason, the determination of the value of free 
 gold-bearing quartz in place, by sampling and assay, is 
 a very uncertain method of fixing the value of a mine, 
 and yet it is the one universally employed by experts, and 
 these experts in general, are entirely unfamiliar with the 
 existing conditions of that particular section, As pre- 
 
HINTS ON AMALGAMATION. 99 
 
 liminary information, sampling of a mine and fire as- 
 says, are very necessary, but before a definite conclusion 
 is arrived at, wherever possible, a practical mill-test 
 of 25 to 100 tons should be employed, the ore for which 
 is taken from all parts of the mine, without sorting, 
 and just as it would be worked permanently on a large 
 scale. If under no circumstances can such a mill test 
 be made, we advise this method of procedure. The ex- 
 pert comes to the property and makes a rapid survey of 
 the interior workings of the mine, and the character of 
 the wall rocks, strike, etc. Then he will examine the 
 general surface geology of the country, and by inquiry 
 and observation, determine the prevailing conditions of 
 that section. This can be seen by the operations of 
 neighboring mines, if there are any that are working 
 or have been exploited. With the deductions he makes, 
 after sifting out notable inaccuracies due to ignorance 
 or jealousy, it is now with a common-sense foundation 
 of the general conditions that he is able to devote his in- 
 quiries to the one mine in view. A few pieces of the ore 
 from different parts are first taken, crushed in a hand 
 mortar, and panned, to determine the character of the 
 gold, whether coarse (when it is probably very un- 
 evenly distributed), or fine and floured, which would 
 imply a more uniform dissemination. Of course, the 
 number of samples taken must be in great abundance, 
 near together, and each of large size, and the maximum 
 distance between samples should not be over 8 to 9 feet. 
 If fine, and several hundred feet of quartz have been 
 exposed, we are generally safe in an average value, if 
 the samples are taken every 20 feet. In every case, 
 each sample must be taken completely across the ledge, 
 either by blast or maul, and everything mixed and quar- 
 tered down to the size required without using any dis 
 
100 HINTS ON AMALGAMATION. 
 
 cretion or selection, as that is the way it would be prac- 
 tically worked in a mill. If practicable, have a small 
 assay crusher, and reduce the coarse uniformly, as the 
 quartering proceeds, thoroughly mixing after each reduc- 
 tion in the size of the pieces. A diagram of the mine 
 where each place is sampled, with its corresponding 
 number, is entered in the note book, and the samples are 
 sacked and sent to the assayer for tests, but each sam- 
 ple should weigh 5 pounds, and 15 pounds is better. We 
 wish to state at this point that the value of a mine is 
 not always determined by sampling, but it is the only 
 resource on which an expert foreign to the conditions 
 of a certain section, can rely for his first judgment 
 of the property, while it is the natural preliminary to a 
 practical mill-test. Should the vein be too large to ad- 
 mit of taking one sample across its width, a series of 
 samples are taken in each cross-section at absolutely 
 equal distances apart in every case. 
 
 After the assayer returns the individual values to the 
 expert, he is able to lay out accurately the length and 
 direction of the ore-shoot or shoots, in the mine, and 
 whether the ledge-matter intervening, has a value that 
 would warrant its exploitation without reducing the 
 total output prohibitively. He now instructs the assayer 
 to take a weighed proportion of each sample, good or 
 bad, that occurs in the ore-shoot, and make a laboratory 
 working-test, on amalgamation and subsequent concen- 
 tration. This will serve as a guide for a final mill test, 
 but only as a guide, as the mechanical work of the mill 
 will generally give better results than any hand-test 
 made, though only in total value saved, and not nec- 
 essarily in an increase of either the free gold or sul- 
 phurets. Unless frequent and large samples from the 
 mine are taken as stated above, the resultant mill work 
 
HINTS ON AMALGAMATION. 101 
 
 will be very disappointing to the owners, and detrimental 
 to the reputation of the expert himself, unless the blame 
 is laid on a supposedly faulty mill. This is frequently 
 done, and very unjustly, if a good amalgamator is in 
 charge. Grab samples of a few selected pieces, judged 
 by the eye, to be both average, poor and the highest 
 grade, can be assayed, and a test of the ore in 25-ton 
 lots run through the mill, and the resulting product be 
 found to be not over 60 per cent, of what was expected 
 from the average of the selected samples, when accusa- 
 tions of dishonesty are hinted at and often expressed. 
 It seems to be an accepted axiom amongst mine owners 
 that "a custom mill will always cheat," when the fault 
 lies entirely with themselves in estimating what ought 
 to be returned, according to the assays of one or two 
 little pieces of rock, and human nature will force them 
 to take, if not the better looking rock, at least, clean ore, 
 neither of which, it is readily seen, can be any criterion 
 of a mass of ledge blasted down and always carrying 
 more or less of the barren country rock which has to 
 be handled with the clean quartz, on wnch they form 
 their judgment. 
 
 I have gone so fully into a matter that does not seem 
 to be pertinent, because, as mentioned above, the mills 
 are generally so unjustly blamed. Several years ago, 
 I was requested by a prominent railroad man, to make 
 a working test in a neighboring mill, on 25 tons of ore 
 from a mine he held under bond. While the ore was 
 being brought to the mill, I was asked to make three 
 assays, one of a highly mineralized piece of rock weigh- 
 ing less than a pound, and supposed to be so high-grade 
 that similar rock was not shipped to the mill, but was 
 sorted out for sale to smelter. The second sample was 
 one piece of about % pound weight, taken from the 
 
102 HINTS ON AMALGAMATION. 
 
 mine and considered about average, while the third sam- 
 ple was their average of this entire lot and consisted of 
 four little pieces of clean quartz. After making the as- 
 says and finding the highest grade did not go over 
 $10 per ton, while the average of the three, even in- 
 cluding this one, was under $8 per ton, I examined the 
 ore that had already been stored in the bin and was 
 positive it would not stand up to the assays. Therefore, 
 to protect myself beforehand, I informed this gentleman 
 that I wished him to bear in mind a common report that 
 custom mills invariably retained a part of the proceeds 
 for their personal aggrandizement. On the completion 
 of the test, the resultant amalgam netted $3.50 per ton, 
 the concentrates $1 per ton, and the final tailings 35c. 
 per ton, giving a total of $4.85 per ton of ore treated. 
 On making my report the question was immediately 
 asked, why the returns were so low, when the average 
 of the preliminary assays showed $8 per ton; but, calling 
 to my help the previous statement and the required ex- 
 planation placed the situation most forcibly before this 
 gentleman. It is, therefore, well to have a most thor- 
 ough sampling of the mine, or trust entirely to the sam- 
 ples taken in the mill. 
 
 Assays during the steady run of a mining property are 
 rarely taken in California, except in the case of foreign 
 corporations, and it is a very great mistake. The ex- 
 pense of an adequate outfit is very slight, at a maximum 
 price of $500, and the cost of all the assays per month, 
 would make no material difference in the profit, while 'n 
 many cases great losses would be prevented. The com- 
 mon practice is to guess at the value of the ore, and the 
 loss in final tailings, by panning. Though it is not im- 
 perative to assay by fire all the ore of a free-gold mine 
 dally, yet an occasional assay of a new stope opened, or 
 
HINTS ON AMALGAMATION. 108 
 
 any change in the character of the quartz is a very 
 great help. This same sample should be panned, 
 and then becomes an approximate guide to the 
 value of the different samples that must be 
 panned down each day by the foreman or in 
 case of a large property, the employe especially appoint- 
 ed for that purpose. In the Homestake property, one 
 man is kept steadily at work panning and estimating 
 the free gold value of over one hundred samples each 
 day. The method employed there, is to weigh out a cer- 
 tain portion of each sample and pulverize it to an im- 
 palpable powder in a hand mortar, filled with water, the 
 crushing being done by a pestle attached to a power drill. 
 The resultant pulp is panned, and the values of the 
 gold judged by the eye alone, is entered in the report 
 book. By constant practice, the accuracy attained on 
 that ore is remarkably correct, but the same man on 
 another property would require several assays before he 
 would become as adept in agreeing so closely. Again, 
 this will give only the free gold, and is of absolutely 
 no value in determining the gross amount of gold in the 
 ore, where a fire assay alone can be of any benefit. 
 Therefore, in regard to the ore in a free-milling prop- 
 erty, be sure and have occasional assays, and do not trust 
 entirely to the. eye. 
 
 Coming down to the mill, we find a very different sit- 
 uation where a very close estimate of the value of the 
 quartz can be obtained, often by taking periodical sam- 
 ples from the self-feeders, and always accurately by 
 samples below the plates and adding to the values of 
 the assays, the amount of free gold collected. 
 
 Several devices for automatic sampling have been in- 
 vented, but from the fact that it is the exception to 
 see any of them employed, it is conceded that ordinary 
 
104 HINTS ON AMALGAMATION. 
 
 hand sampling is as correct, gives less trouble, and is 
 always available. Hand sampling has its points to be 
 observed to insure accuracy and very few appreciate 
 the wherefore that it should be done in one way more 
 than another. To get a sample of the quartz before 
 entering the battery, it must be taken as it leaves the 
 feeder to enter the throat of the mortar. Use a dipper, 
 and see that the same quantity each time drops into it. 
 Be sure and be regular in time, either a half-hour or 
 hour, that each sample is taken, and at the end of the 
 specified number of hours, reduce the whole systematic- 
 ally by finer crushing, mixing and quartering. The 
 reason that the outlet of the self-feeder is the only safe 
 place, is that the ore is here the most thoroughly mixed 
 and crushed to a more uniform size. Carcamples aie 
 only grab samples, a little taken at random from the top, 
 generally the finer pieces, or, if a coarse piece is taken, 
 too great a proportion for that time. From the car 
 the ore is separated by the grizzly into the fines and 
 coarse, but the coarse is broken by the crusher, and, 
 in passing through the ore bin. becomes fairly well 
 mixed with the fines. It is then remixed in passing 
 through the automatic feeder, and, being delivered by 
 that to the battery in such a small quantity and thin 
 stream, all of the ore for that instant is caught in each 
 sample. We consider this sample of small importance, 
 as we get immediate returns from the free gold, and it is 
 only the value locked up in the sulphurets that would 
 probably escape us, which we can only determine after 
 the free gold is extracted. Therefore, the important 
 sampling begins at the end of the plate surface. We 
 have two places at our command, at the inlet and at the 
 outlet of the trap. It is unsafe to trust a sample taken 
 below the lower apron plate as there is always the pos- 
 
HINTS ON AMALGAMATION. 105 
 
 sibility of a little amalgam being broken off in passing 
 the dipper along the edge of the plate. If it can be done 
 and the whole stream covered, the inlet to the trap is the 
 better place, as the outlet may carry more sulphurets 
 than the average at one time or the other. The under- 
 current will accumulate sulphurets to a ceratin depth, 
 when the increased pressure will throw them out in a 
 bunch, and the process is begun over again. In taking 
 all these samples, a separate dipper must be kept for 
 pulp, as well as for tailings. No overflow whatever is 
 allowed, and the sample is put in a covered can, while 
 the dipper is thoroughly rinsed out each time. The 
 jar of the mill will very rapidly settle all the solid matter 
 when the clear water is very carefully poured off, al- 
 lowing none of the slimes to escape. In very exceptional 
 cases it will be advisable to evaporate all this water 
 for a comparative test, but the difference will be found 
 to be imappreciable. At the end of the time set, the 
 resultant sample is thoroughly dried, mixed, quartered 
 down and assayed. Should a regular daily assay be 
 made, which will give a correct weekly average, it is 
 only necessary after pouring off the supernatant liquid, 
 to mix most thoroughly the residual slimes into a con- 
 sistent mass, and then, while stirring, take out a dip- 
 perful and dry that for the assay. 
 
 The most important sample, and the only one abso- 
 lutely necessary in a gold mill, is that of the tailings as 
 they leave the mill. These should be taken each hour 
 from the foot of each machine, and never, under any 
 circumstances, from the waste sluice where there might 
 be a partial reconcentration of the tailings. The dipper 
 is drawn steadily across the foot with no pause at either 
 end where a great proportion of the tailings leave the 
 machine. This sample is settled and manipulated as 
 
106 HINTS ON AMALGAMATION. 
 
 \ 
 
 described for the pulp, but at the time each one is 
 taken, a duplicate should be examined by panning, to 
 see the amount of visible sulphurets escaping. The fore- 
 man should compare the assays of a sample with a 
 panning test of the same, and after several examples 
 can approximately determine tLe good or bad working of 
 any particular machine, from panning alone. In mak- 
 ing these tests, the color of the sulphurets are so different 
 
 Modern Machinery. FIG. 27. 
 
 from that of gold, that they do not show on a dark 
 ground, and they are so fine and light that more care 
 must be exercised, and, in reality, a different method 
 employed. The best color is pure white, and where 
 nothing better offers, a tea-saucer is far preferable to 
 a gold-pan. However, now, there can be procured white 
 enameled pans of all sizes, but choose those with very 
 flaring sides. A patented instrument is now specially 
 
HINTS ON AMALGAMATION. 107 
 
 made, by which the faintest trace of sulphuret can be 
 detected. The idea originated from the Cornish van- 
 ning shovel, used in the tin mines, where all assays are 
 made by hand concentration of the sample. Similar 
 in shape to an ornamental plaque, it is called a vanning 
 plaque. It is a circular segment of the surface of a 
 globe, and is made of wrought iron, covered with a 
 homogeneous coating on both sides of white enamel. 
 The method of using this is different from that of a 
 pan or saucer, in that the plaque is always held nearly 
 horizontal. The tailings are settled by swinging it hori- 
 zontally and then allowing a wave of clear water to pass 
 over the surface with this same circular motion. When 
 the tailings have been reduced to a minimum without any 
 loss, the plaque is held firmly in the two hands at a steep 
 angle, and by a series of jerky throws, the heavy sul- 
 phurets climb up the inclined plane, and can then be 
 collected in a string of colors by gently washing the re- 
 maining sand away. (Figure 27.) 
 
 In regard to the concentrates, the only reliable assay 
 is of the bulk when prepared for shipment, but a close 
 approximation can be obtained by taking numerous sam- 
 ples with the butter-trier or augur, from the settling box 
 in front of the machine, after the water has been re- 
 moved. It is unsafe to make any definite conclusion 
 from a sample taken off the belt. 
 
CHAPTER VII. 
 CONCLUSION. 
 
 With the suggestions in the foregoing pages taken .~s 
 a basis, it should not be difficult for any one to adapt 
 them to the local conditions so as to increase the efficien- 
 cy of the work, and to correct unknown losses. Put 
 in a concise form, the summary would be. 
 
 1st. Beware of grease. 
 
 2nd. Amalgamate dry. 
 
 3rd. Turn over the pulp as frequently as possible 
 near the battery. 
 
 4th. Use all necessary water inside the battery, and 
 do not divide it with a spray outside. 
 
 5th. Have the battery water warm, at least above 
 a minimum temperature of 50 degrees, better above 70 
 degrees. 
 
 6th. Use no acids on the plates,, nor lye or cyanide 
 inside the battery. 
 
 7th. Dress the plates at least one a day, but remove 
 as little of the amalgam as can be prevented till clean-up. 
 
 8th. Most thoroughly clean the daily amalgam at once. 
 
 9th. Systematize regular clean-ups and do not remove 
 unnecessary dies. 
 
 10th. Retort out of doors and do not use charcoal or 
 coke for fuel. 
 
 llth. See that the concentrators work noiselessly and 
 without a jar. 
 
 12th. Watch the tailings of the concentrators and see 
 that the loss from the mill is kept at a minimum. 
 
 108 
 
HINTS ON AMALGAMATION. 109 
 
 13th. Be very sure that your ore is adapted to the 
 free-milling process. 
 
 (All gold-bearing ore is not adapted to the free-milling 
 process, and on opening a mine this point must be defi- 
 nitely determined before the reduction works are erected. 
 An assay will determine the value, a panning test will 
 demonstrate if any of the gold is free, and a laboratory 
 working test will inform us of the amount that can be 
 expected to be saved by amalgamation and concentra- 
 tion; but if the final tailings are still very high, some 
 method has to be found to recover this value. Should 
 the highest percentage remain in the tailings, cyaniding 
 must be tried, or chlorination, if the gross value of the 
 ore will stand the expense, while sometimes a combina- 
 tion of all must be used. If the ore is very high-grade 
 and refractory as well, smelting of the mass is the 
 proper procedure. Neither cyanogen or chlorine will 
 economically act on coarse gold, and both processes 
 require crushing. If our panning tests show coarse gold, 
 and the value is too low for smelting, we have to crush, 
 and then, either before or after the chemical work, can 
 secure the coarse gold by amalgamation. The great- 
 est detriment to successful milling is the presence of tel- 
 lurium compounds, except the telluride of lead and cop- 
 per. These cannot be amalgamated or concentrated to 
 a practical efficiency, and yet if these ores as usual, show 
 great richness in free gold and coarse gold, they are 
 milled, and, as a consequence, hundreds of thousands of 
 dollars are run to waste, all of which would have been 
 saved if the whole mass had been shipped to a smelter. 
 Therefore, examine the ore for tellurium, and if of suf- 
 ficient richness, ship, even though at the same time rich 
 in free gold. 
 
 In Tuolumne County, California, many of the mines 
 
110 HINTS ON AMALGAMATION. 
 
 have chimneys of ore very rich in free gold and tellurides, j 
 and the early history of a few of them, show that they" 
 were formerly abandoned, though known to be rich, 
 because so little of the value could be saved. One mine 
 can be specially mentioned as a type, namely, the Black 
 Oak. This mine very nearly ruined its owners, by the 
 attempt to work by free-milling alone, was bonded twice 
 and abandoned, and within two years from this time, 
 had been offered on long bond for a small figure. To- 
 day, it cannot be bought, since means have been found to 
 save the $10 to $50 per ton previously lost. No special 
 method has been devised, but reduction was at last 
 adapted to common sense. Instead of using the mill 
 process as the sine qua non, the ore is now partially sort- 
 ed, the richest shipped direct to the smelter, the balance 
 crushed wet by mill, amalgamated and concentrated. 
 !_The. tailings are impounded and worked by cyanide pro- 
 cess, and the concentrates shipped to smelter. 
 
 On ores which are purely adapted to concentration, it 
 becomes very frequently a delicate question whether to 
 employ stamps or some other crushing device. In this 
 case, the object is to have the grains of sulphurets, while 
 absolutely freed from the gangue, in as large a size as 
 possible, and with a minimum of slimes. Stamp mills 
 for amalgamating, make a larger proportion of slimed 
 mineral than Cornish rolls and devices of the type of the 
 Chilian mill, for the reason that the pulp will escape 
 from the latter forms, as soon as crushed to the re- 
 quired fineness, while, owing to the height of discharge 
 in a stamp mill, quite a proportion is struck several 
 times before escaping. Here the character of the ore can 
 be divided into two classes: Class A, in which, if it 
 is found that the ore carries enough free gold to pay 
 working expenses, the process as minutely described in 
 
HINTS ON AMALGAMATION. Ill 
 
 the foregoing pages must be employed; class B, in 
 which the ore contains no free gold of moment. Stamps 
 are employed on hard ore in which the mineral is finely 
 disseminated through the matrix. The discharge is in- 
 stantaneous, and the mortar, being merely a crushing de- 
 vice, is patterned after that in use in silver mills. If the 
 ore is soft and shows great tendency to slime, roller mills 
 are the proper machines with vanners to do the concen- 
 trating. ' 
 
 The subject is endless, and as a science, gold metal- 
 lurgy is still in its infancy. However, we trust that the 
 above hints will be of some help in the one branch 
 of this science that has been considered in these pages. 
 
 UNIVERSITY 
 
 CALIFOH 
 
 THE END. 
 

m 
 
 
 UNIVERSITY OP CALIFORNIA 
 LIBRARY 
 
 ^EK$~#fTB DATE. 
 
 This is the date on which this 
 book was charged out. 
 
 
. 
 
 
 550