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*The amalsamating apparatus in the mills marked with the asterisk is given below. † C. copper-plate. C. & A. copper-plate and arrastra, W. & S. water and steam. § A. arrastra.

In numbers 5, 6, 11, 12, 14, 25, 30, and 40 the average yield is obtained by divid ing the sum of two figures given by Mr. Rémond. For instance, the average yield of mine No. 5 is given above as $32 50, whereas Mr. Rémond s the yield is from $25 to $40. In the same manner the cost of extraction in No. 37 is given at $4 374, whereas Mr. Rémond says it is from $2 75 to $6. M ines Nos. 59 and 70 yield coarse gold, which is taken from the rock after Pounding it in a hand-mortar.

say

In mill No. 11 Hungarian pans are used, and in No. 12 Hungarian pans and a arrastra;'in No. 13, Patterson's pans and separators; in No. 14, copper plates and amalgamating pans; in No. 15, Salmon's amalgamator and Salmon's eparator; in No. 23, copper plates, an arrastra, a Beath's grinder and a Saln on's concentrator; in Nos. 26 and 37, copper plates andb lankets; in No. 27, acentrifugal grinder, a Ryerson's pulverizer, a super-heated steam apparatus, and a shaking table; in No. 28, shaking pans and a Chili mill; in No. 29, .. copper plates, shaking pans, and an arrastra; in No. 30, cast-iron barrels; in No. 31, copper plates and a shaking pan; in No. 32, copper plates, arrastras, and a shaking table; in No. 34, an Ambler's concentrator, a shaking table, and arrastras; in No. 35, copper plates and a Beath's amalgamator; in No. 45, Varney's pans and a concentrator; in Nos. 66 and 67, copper plates and Knox's pans; in No. 71, copper plates, a Farrand's amalgamator, and a settler; in No. 73, Varney's pans and a settler, and in No. 82, copper plates, shaking tables, and an arrastra.

It appears that the average thickness of 21 lodes is from 1 to 12 inches, inclusive; in 20, from 13 to 24 inches, inclusive; of 9, from 25 to 36 inches,

Power used; water or

steam.

Number of stamps.

Kind of amalgamating
machinery.

Cost of roads.

Cost of ditches and

flumes.

inclusive; of 10, from 37 to 48 inches, inclusive; of 9, from 5 to 10 feet, inclusive; and of 2, over 10 feet.

In 9 mines the average yield is under $10 per ton; in 22 it is between $10 and $19, inclusive; in 14 it is between $20 and $29, inclusive; in 14 it is between $30 and $49, inclusive; in 3 it is between $50 and $69, inclusive, and in 4 it is over $70. Only one mine has a yield as low as $4; three have a yield of $6; 4 of $8, and 1 of $9.

The cost of extraction per ton depends, to a considerable extent, upon the thickness of the vein, or, rather, of the pay-rock in the vein. In mine No. 48 the vein is only two inches thick, and it costs $60 to get out a ton of ore, while in No. 62 it costs only 50 cents to take out a ton of rock from a vein 15 feet wide. In 1 mine the cost of extraction was under $1; in 8, between $1 and $1 90, inclusive; in 14, between $2 and $2 90, inclusive; in 9, between $3 and $3 90, inclusive; in 9, between $4 and $4 90, inclusive; in 7, between $5 and $9 90, inclusive, and in 7, $10 or more.

In 16 mines there is no cost of transportation of ore to mill, the extraction covering that expense; in 23 mines the cost is less than 90 cents; in 7 mines it is between $1 and $1 90, inclusive; in 6 it is $2 or more.

In 1 mill the cost of treatment is 75 cents; in 14 mills it is from $1 to $1 90, inclusive; in 19 it is from $2 to $2 90, inclusive; in 9 it is from $3 to $3 90, inclusive, and in 9 it is $4 or more. The richer the rock, as a general rule, the more expensive the treatment. The quartz of mine No. 48, yielding $180 to the ton, costs $7 for treatment

Of the mills visited by Mr. Rémond in 1865, 38 were not running, 25 were running, 2 were ruined, and 2 were unfinished. Of those not running, some were standing idle for want of water, others had exhausted the pay-rock within sight and were preparing for further explorations, and the owners of a thirdclass had no expectation of resuming work, having found it unprofitable, but hoped to sell or intended to move their machinery.

The cost of each of 11 mills was under $2,900; of 20 mills it was between $3,000 and $3,900, inclusive; of 14 it was between $5,000 and $9,000, inclusive, and of 14 it was $10,000 or more.

The number of stamps in 10 mills was 4 or less; in 22 mills, between 5 and 9, inclusive; in 20 mills, between 10 and 14, inclusive; in 10 mills, 15 or more. The power in 52 mills is water; in 11 mills, steam; in 3, water and steam. In 31 mills copper plates were used alone for amalgamating, (outside of the battery;) in 3 the arrastra was used alone; in 7, copper plates and arrastra ; and in 26, other devices, with or without copper plates or arrastras.

At 25 mills the roads cost less than $1,000 for each; at 12 mills, between $1,000 and $1,900, inclusive; at 4 mills, between $2,000 and $2,500, inclusive; at 1, $6,500; and at 15, nothing.

At each of 21 mills the ditches and flumes cost less than $1,000; at 13 mills the cost was between $1,000 and $1,900, inclusive; at 3, between $2,000 and $3,900, inclusive; at 3, $4,000 or more; and at 14, nothing.

The county assessor of Nevada county, California, reported the statistics of the quartz mines and mills of Grass valley and Nevada for the year ending October 1, 1866, as follows:

List of quartz mines at Nevada City and Grass valley.

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Grass valley is the most productive gold-quartz mining district in the world. The annual yield of an area drawn by a radius of four miles is $3,500,000. The number of laborers employed in the mines and mills is 2,000, showing an average yearly production for each person of $1,750, and the average yield of the rock worked is $30 to $35. The lodes are narrow, none of them exceeding seven feet in width, and most being less than a foot. They contain much pyrites, and this fact contributes with the narrowness of the veins to make the average expense of extraction and reduction high-about $15 per ton. Some of the works have been sunk to a depth of 400 feet, but most of the pay-quartz is obtained within 200 feet of the surface.

9.-PULVERIZATION OF QUARTZ.

The main processes of quartz mining are extraction, crushing, and amalgamation. The extraction of auriferous quartz from the vein is like that of ores generally. Any person familiar with copper mining can in a few days learn to be a good gold miner. The quantity of copper ore can usually be discovered by a glance, but in auriferous quartz it is often necessary to pulverize a piece of the quartz, and wash the powder in a spoon or little basin to see whether it will pay to extract. The cost of tunnels and shafts for opening mines in such rock as is usually found about the auriferous lodes is from ten to fifteen dollars per lineal foot.

Ninety-five per cent. of all the crushing in California is done with stamps. The stamp is a block of iron, weighing from 300 to 1,500 pounds, fastened to a wooden or iron shaft, usually iron. A battery consists of several stamps standing side by side, and in most mills the number of stamps is five or a multiple

of five. The stamps are successively lifted by machinery, and then allowed to fall on the quartz. The height to which they are raised is from ten to fifteen inches, and each stamp falls from forty to eighty times in a minute. It is calculated that each stamp should crush a ton of quartz of ordinary quality in twenty-four hours. The mills usually run night and day. Of course, the amount of quartz crushed depends to a considerable extent on the hardness of the rock, the weight of the stamp, the height of the fall and the rapidity of the blows.

The fineness to which the rock must be pulverized depends on circumstances. The particles of gold may be very fine, so that the quartz must be reduced to an impalpable powder before they can be liberated; but if the particles of gold and the grain of the rock are coarse, or if the pulp is to go through a grinding pan, the quartz may quartz may be allowed to escape when many of the particles are as coarse as sea-sand, or even coarser. The battery has on one side a screen of wire-cloth, or perforated sheet iron, with apertures of the size of the largest particles that must be permitted to escape. A steady current of water runs through the battery, so as to carry away the quartz dust as soon as it is fine enough. The sheet-iron screens are punched with needles, and are known by the numbers. No. 7 screen is punched with a cambric needle; Nos. 3 with a darning needle.

In Grass valley most of the mills use Nos. 3 and 4 screens; elsewhere Nos. Nos. 4 and 5 and 6 are preferred.

A multitude of crushers have been tried to break up the quartz before it is given to the stamps or other pulverizing apparatus, but the number in use is very small. Those principally in use consist of two heavy iron jaws, which are wide apart at the top, and close together at the bottom, and as they work back and forth, the quartz is smashed between them. The quartz is usually in pieces. not larger than goose eggs when delivered to the battery, and it is broken this size either by sledge-hammers, or by a large stamp, kept for the purpose of breaking up the large stones.

The musket-ball pulverizer has been tried as a substitute for stamps, and the report is favorable, but the trial has not been sufficient to command the confidence of miners. It is an iron barrel which revolves twenty-four times per minute on a longitudinal, horizontal axis. Inside of the barrel are a number of chilled iron balls weighing an ounce each. The quartz is introduced in particles not larger than a grain of wheat, and in two hours it is reduced to an impalpable powder.

Another pulverizer, that has been tried without attaining favor, is an iron star or wheel without a rim, which makes 1,000 or 1,500 revolutions per minute in an iron casing. The quartz is thrown with great force by the arms against the casing and is dashed into fragments by the concussion. The casing is so made with little offsets that the quartz strikes at right angles.

10.-AMALGAMATION OF GOLD.

Much of the gold is caught or amalgamated in the battery. The stamps fall into an iron box or mortar, into which an ounce of quicksilver is thrown for every ounce of gold supposed to be in the quartz. If the rock is crushed fine in the battery, two-thirds or three-fourths of all the gold saved may be caught there, leaving one-third or one-fourth that escapes through the screen.

After leaving the battery, the pulverized quartz in most mills runs down over copper plate which has been washed over with diluted nitric acid, and then rubbed with quicksilver till the whole surface is covered with amalgam. The particles of gold running over this surface adhere and form amalgam; and when the plate is covered with gold it operates far more effectually than when the quicksilver is fresh. Gold unites more readily with gold amalgam than with pure quicksilver. The copper plate, which is the bottom of a trough or sluice, may be fifty or a hundred feet long. Küstel in his book on Nevada and Cali

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