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fornia processes of silver and gold extraction (page 16) says, copper plates as a means of amalgamation are "very imperfect and mostly abandoned. Imperfect they may be, but they are still used in most of the quartz mills of the State; and in some of the best, or at least in some of those which produce the largest amounts of bullion.

Between the copper plates in many mills are troughs in the bottom of which are laid coarse blankets, or gunny-bag, or even cow hide with the hair on and the grain against the stream. Gold amalgam and sulphurets are caught in the rough surface of the blanket, gunny-sack, or hide, which must be taken up and washed at intervals, which are usually not more than half an hour long.

The shaking table used in amalgamation is a long box with transverse divisions containing quicksilver. It is set horizontally and is shaken longitudinally, receiving from 100 to 200 short jerks in a minute. By these jerks the pulp is thrown back upon the quicksilver.

At the Hayward mine the pulp runs out from the amalgamating battery over a wide pine board, across the grain, and the appearance of the amalgam on this board is supposed to give the best indication whether the proper quantity of quicksilver is being used in the battery. If too much, most of the amalgam runs off, and the little caught on the board is in brilliant round globules, and if not enough, the amalgam has a rusty look.

The arrastra is extensively used for amalgamating, and it has the merits of cheapness, grinding well, adaptability to any place, kind of power, economy of water, and facility of working; but it is slow, and is therefore not in favor in large mills.

Atwood's amalgamator, used in many mills at Grass valley, consists of level troughs, with quicksilver at the bottom; and over the troughs are horizontal revolving cylinders with projecting spikes, which stir up the quicksilver and the pulp as the latter passes over the trough.

Pans are coming into use slowly in the gold quartz mills—at least in some of the new ones lately erected in Grass valley. Küstel says of pan amalgamation that it is "at present the most perfect gold manipulation," and by it "gold is extracted as close as ninety-five per cent. of the fire assay"—that is, if there are no sulphurets. (Nevada and California processes, page 63.) The general opinion is that from twenty to forty per cent. of the gold is lost in the ordinary processes. The pans used are mostly like those that will be described as being used in the silver mills of Nevada. There is, however, one pan not used for silver reduction that has found some favor with gold miners. This is Baux and Guiod's pan, which has a tight fitting cover. The pulp runs constantly with a stream of water down into the pan through a tube at the side, and the light matter after being ground runs up and out through a tube in the centre. There is thus a constant feed and discharge, while in nearly all the other pans a batch of ore is put in and worked, and then taken out to make room for another batch.

The Ryerson amalgamator is an air-tight chamber in which quartz that has been crushed very fine by some dry process is subjected to the influence of super-heated steam for half an hour as a preparation for the quicksilver, which is then introduced and converted by the heat into a vapor, in which form it is supposed to pervade the pulp and get access to all the gold. Cold water is injected to condense the quicksilver, and the pulp is drawn up to be separated.

11.-SULPHURETS AND CONCENTRATION.

But after the pulp has passed through all the amalgamating processes customary in gold quartz mills, it is found that in many ores much of the gold is lost because of the presence of sulphurets of iron and copper. The presence of the sulphurets appears to chill the quicksilver and prevent it from taking hold of the gold, and many particles of gold appear to be enveloped by them. The

gold can be separated from the pyrites, but heretofore the separation has been affected mainly in establishments specially devoted to that purpose, and not in the ordinary mills. It is customary to save the sulphurets and sell them to the sulphuret works, or keep them until there may be a sale for them. But for the purpose of saving them, they must be separated from the earthy and rocky matter in the pulp, and this is called concentration. The sulphurets have a specific gravity of 4.5, while quartz has a specific gravity of 2.6. By this difference in density, it is possible to separate the two.

There are several patent concentrators in use, all made of iron, and shaped like shallow pans. The one more used than any other has a bottom that rises from the edge to the centre, where there is an outlet through which the lighter material runs away. This outlet is, of course, not so high as the rim. This pan turns on a perpendicular axis, and is shaken back and forth by two hundred short jerks per minute. A hole in the side is left open for the escape of the sulphurets, which flow out in a steady stream; and lower down is another hole, which is opened when the heavier matter is to be taken out.

One of the best cheap concentrators is a long and wide rocker with a flatbottom and a slight inclination. A boy can work one of these concentrating rockers for a large mill, and the cheapness of the machine and the slight power required for it are great advantages. The sulphurets are arrested by cleets in the bottom of the rocker, and need to be taken out at intervals of half an hour. Any sluice serves also, to some extent, for concentration.

12.-CHLORINATION.

The most approved method of reducing auriferous sulphurets is chlorination. As a preparation for this process the sulphurets are roasted. They are placed in an oven brought to a red heat, retained in that condition for about six hours, or until the smell of sulphur has disappeared. After they have cooled the sulphurets are sprinkled with water, shovelled over, and put into wooden tubs or boxes, so made that chlorine gas can be introduced at the bottom and made to rise all through the mass. The tub or box is kept closely covered, and chloride of gold, which is soluble in water, is formed. After the lapse of four or five hours water is let in, and the chloride of gold is dissolved by it; the sclution is drawn off into glass vessels, and some sheets of iron are put in; the chlorine unites with the iron, and the gold falls as a purplish-brown powder to the bottom of the vessel.

13.-GOLD IN LOOSE STATE.

Gold mines are divided into the two main classes of quartz and placer, but at Whiskey Hill, near the town of Lincoln, in Placer county, about thirty miles, from Sacramento, a large mass of loose slate rock is found, containing considerable pyrites and about six dollars of gold to the ton. The material is so soft that eight tons can be crushed by a stamp in a day. It is supposed that below the water-line a vein of hard auriferous copper ore will be found. The mass of auriferous slate in the hill is large, and the mine is considered very valuable, one-half of it having been sold for $175,000. Similar bodies of auriferous slate mixed with clay are found at Lander's ranch, Placer county, and at Telegraph City, in Calaveras county.

14.-PLACERS.

Placer mining is decreasing every year. Every month witnesses the exhaustion of some rich placer district, or its exhaustion at least for the present. It may be that in the future, when laborers can be employed for fifty cents per day, claims which cannot be worked now will be in demand.

There are large bodies of gravel that contain just gold enough not to pay,

at the present rates of water and labor, and it is evident that both must be cheaper after the lapse of a few years.

But although land might pay the miner, it may pay the farmer still better, and the State should give every preference to the latter, who beautifies and enriches the soil, while the miner destroys it.

Notwithstanding the continuous decline of the placer mining interest for ten years past, there are yet, and long will be, very rich placers. Some of the deposits of gold in clay and gravel are so protected that a score of years may elapse before they can be reached. On the sides and near the base of the Sierra Nevada are innumerable hills that are destined to come down before the hydraulic pipe of the miner. One of these hills commences near the town of You Bet, in Nevada county, and extends sixteen miles up the mountain side, with a height of two hundred feet, and a width of a mile; and there is reason to believe that the foundation throughout its length is a bed of rich auriferous cement.

15.-CEMENT MINING.

The cement deposit is a stratum of very tough clay enclosing gravel and boulders; and the clay is so stubborn that it will not dissolve in a sluice-box, and it has been necessary to crush it in mills. The material is heterogeneous ; the clay is soft under the stamp; some of the gravel is hard, and other soft. The gravel is not auriferous, but it must be crushed, so as to permit the crushing of the clay. Several attempts have been made to separate the stones from the remainder of the mass without crushing them, but without success. As the stones contain no gold, all the power spent in crushing them is lost; but at present there is no other way, nor is it probable that any mode of separation can be devised. One stamp will crush from four to six tons of cement per day, and the cement stamps are only about half as heavy as quartz stamps. The pulverization is not so fine as in quartz; the sheet-iron screen through which the cement pulp escapes is punched with holes that vary from a sixteenth to an eighth of an inch in size. The particles of clay that escape are so small that they are easily dissolved in the water. The gold is caught in the battery, and that which escapes through the screen is caught in the sluice. It is a singular fact that many of the hills of the present day stand upon the beds and precisely indicate the course of the streams of a former geological epoch. The existence of a layer of basalt or volcanic rock along the top of these hills indicates that currents of lava followed the streams, and after hardening protected the gravel under them from being washed away by the great aqueous agencies which wore down the rock and earth in the neighborhood to a depth of more than two thousand feet in some places. So common are auriferous channels under the hills that the term "rim rock" has long been in common use among miners to indicate that part of the bed rock which separates the lowest portions of the channel from the outside of the hill on both sides. In some districts it is taken for granted that if a tunnel is cut into a basalt-covered hill at the proper elevation the channel of the ancient river will be found.

16.-HYDRAULIC MINING.

Most of the placer gold of California is obtained by hydraulic mining; the most profitable placer claims, as a class, are those worked by the hydraulic process; and the most prosperous mining counties are those which have the largest areas suitable for piping. The yield in some of the claims is as $100 per day to the hand, and occasionally twice or thrice as much, but the average is probably $10 or $15, of which about half goes to pay for wages, water, and other expenses.

H. Ex. Doc 29-5

17.-RIVER MINING.

Nearly all the river beds have been washed, but they are washed over and over again. The rivers are to be regarded as large sluices into which all the fine gold that escapes from the adjacent mining operations is carried and deposited; and thus there are some river beds that pay for a short time to wash every year. The yield, however, is not large, and miners take to the rivers only as a last resort.

In Trinity and Klamath counties, California, there is a large area of ground that is comparatively undeveloped; and that is the best region in the State for the miner who wants to work on his own account, and on a small scale. The country is rugged, the climate wet and cold, the roads bad, and there is some danger of Indians; but on the other hand there is much gold to reward the skilful miner who is willing to face the hardships and dangers of the place.

18.—THE HAYWARD QUARTZ MINE.

The Hayward claim is one of the notable mines of California. It is situated on Sutter creek, Amador county. The vein is peculiar in its character.

The quartz is in places almost a powder, and is mixed with slate and clay. The length of the ground worked is about one hundred and sixty yards, and both north and south the vein seems almost to disappear. The average yield of the rock is not high, although some very rich and beautiful specimens have been found in it. The mine has been worked since 1851, and the rock has always given a good average yield, but it is during the last eight years that the mine has risen to much importance. The total product is stated to be $6,000,000. The yield per ton and the width of the vein have been gradually increasing, and now at a depth of 1,200 feet the former is $25, and the latter twenty-five feet. The works are by far the deepest in the State, and as the mouth of the mine is estimated to be nine hundred feet above the sea, the lowest works must be three hundred below the surface of the ocean. Professor Whitney speaks thus of the mine, in the first volume of his geological report, written several years ago: "The vein is enclosed in a dark-colored, rather soft argillaceous slate. In the Eureka the mass of vein stone is from eight to twenty feet wide, but in the Badger it widens out suddenly to forty feet.

"The length of ground worked in both mines is about four hundred and seventy feet; to the south of the Badger shaft, which is on the south end of the mine, there is hardly any quartz to be seen, and the lode, which is eight feet wide on the north side of the Eureka, pinches out very rapidly in that direction, so that the body of quartz worked is very short in proportion to its great width, being almost a column, or chimney, rather than a vein. At the junction of the two veins there is a large mass of slate and soft clay mixed with a little quartz, which is often in a state of fine powder.

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"Few if any mines in the State have been more uniformly and permanently successful, while the yield of gold to the ton of rock stamped is quite low."

19.-SIERRA BUTTES MINE.

The Sierra Buttes quartz mine is one of the most noted and most valuable mines in the State. It is situated at an elevation of 6,000 feet, on the southwestern slope of the Downieville Butte, and twelve miles from the town of Downieville. There are two lodes, but most of the auriferous rock is obtained from the cliff ledge, which averages about twenty feet in width, and of this about eleven feet in thickness on an average are worked. In some places the pay streak is only two feet wide, in others seventeen. The average yield of the quartz is about eighteen dollars per ton.

The quartz is bluish white in color, and is very hard when first taken out,

but it crumbles after having been exposed to the air for a time. The gold is disseminated in small particles through the rock, and in most of the quartz the metal is scarcely visible to the naked eye. There are few sulphurets, and therefore amalgamation is easy. About two-thirds of the gold is caught with quicksilver in the batteries, after leaving which the pulverized quartz is carried by water over about a hundred feet of copper plate covered with quicksilver, and then over a blanket, below which are some arrastras which are owned by different parties who pay for the tailings and the water.

The following is an authentic statement of the annual yield, expenses, and dividends since the mine came into the possession of the present company:

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No assessments have ever been levied. The produce of the mine has paid for all the improvements. The yield in 1866 is better than ever; and the character of the lode has remained almost the same wherever they have worked it, without notable difference between the surface and the deepest workings.

20.-THE ALLISON MINE, &c.

The Allison mine at Grass valley is one of the richest and most productive in the State. It has been worked with almost uniform profit for ten years. The average thickness of the lode is about eighteen inches, and the rock yields from $30 to $150 per ton. According to the best information obtainable by the State geological survey 14,858 tons were reduced between March, 1857, and December, 1861, and the average yield was $50 per ton or $942,900 in all. Since the summer of 1862 the mine pays better than before. The lowest workings are nearly 500 feet deep, and the lode at that depth is three feet wide, with rock that averages $100 to the ton. The owners refuse to give any statements of their receipts or expenditures, but the men employed in the mill say the yield is $40,000 per month, or $400,000 for ten months' work in a year; and of this sum two-thirds or more is clear profit. The claim has been worked for a length of about 1,400 feet.

The Norambagua mine at Grass valley has yielded more than half a million dollars in the last five years. The average yield of the ore is about $75 per ton. The deepest workings are 500 feet from the surface, and drifts have been run 1,000 feet along the course of the lode.

The following is a statement of the operations of the Eureka mine at Grass valley for the year ending September 30, 1866 :

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