SAN FRANCISCO, November 17, 1886.

To Honorable GEORGE STONEMAN, Governor of the State of California:

SIR: In accordance with the Act of the Legislature entitled "An Act to provide for the establishment and maintenance of a Mining Bureau," approved April 16, 1880, I herewith transmit my report.

Very respectfully,

October 1, 1886.

REPORT OF STATE MINERALOGIST.

On the first day of June, 1886, the present State Mineralogist was commissioned by his Excellency George Stoneman, Governor of the State of California, vice Henry G. Hanks, Esq., resigned.

Upon assuming the duties pertaining to the office, as prescribed by the Act of the Legislature entitled "An Act to provide for the establishment and maintenance of a Mining Bureau," approved April 16, 1880, the State Mineralogist, upon conferring with the Trustees of the State Mining Bureau, deemed it advisable to obtain such information concerning some of the leading quartz mines carrying on operations on the great auriferous belt of the State, giving such information as would be of interest to the people of the State, and particularly to those persons who are engaged in gold-quartz mining.

The time, during which the State Mineralogist was expected to give his attention to this subject, was so limited that it became impossible to gather much information or many statistics relating to this great industry of the State.

A few of the leading mines, in several of the counties, were visited in person by the State Mineralogist, and he was enabled to collect some data and gather other information from persons familiar with sections of the State which the State Mineralogist was not enabled to visit, who cheerfully gave descriptions of mining operations which were being carried on.

A number of the leading gold mines were necessarily omitted, as well as most of the mines and prospects, which are said to have a promising future. He hopes that in some future annual report he will be enabled to give a full and complete description of the condition of gold and silver mining throughout the entire State, and not be compelled to neglect a description of the localities of other valuable mineral products which exist so abundantly in California, and to report what developments are being made.

It was suggested by the Board of Trustees, that considering the shortness of time in which he would be justified in leaving the Bureau to make his observations, it would be better to chiefly confine his report to a short description of the developments made and the depths of some of the mines, and give such statistics as he could collate, showing the method of extracting the gold and description of the machinery in use.

The grade of the ore being worked in any of the mines visited by the State Mineralogist is not given, for the reason that the mine owners, in common with persons engaged in commercial business or other economic enterprises, do not wish their private affairs given to the public, and do not care to invite any inspection or publication of their books.

The State Mineralogist desires to acknowledge his appreciation of the uniform courtesy and assistance which has been rendered him by the Trustees. The Bureau is greatly indebted to J. Z. Davis, Esq., the Chairman of the Board of Trustees, who daily gives a portion of his time to its progMr. Davis has the success of the Bureau at heart, and has presented many valuable ores and minerals, besides several cases of interesting conchological specimens, and many other attractive exhibits.

ress.

THE MOTHER LODE.

This very remarkable auriferous belt runs in a northwesterly and southeasterly direction, and can be traced for about one hundred miles, from the Mariposa estate, in Mariposa County, through the counties of Tuolumne, Calaveras, Amador, and into the county of El Dorado. The lode dips to the eastward at an angle of from 45° to 70° to the horizon. The walls are uniform and the gouge well defined; the vein matter is white and banded quartz, carrying a small percentage of sulphurets. The eastern, or hanging-wall, is greenstone, and the western, or foot-wall, is slate.

Professor Whitney remarks of this lode:

It is not by any means a continuous bed or vein of quartz, but rather a series of nearly parallel belts of lenticular masses with barren intervals between them, but yet arranged nearly in the same course.

R. H. Stretch says:

The mother lode is not, strictly speaking, a continuous vein, but rather a belt of goldbearing rocks, situated in a line of contact between black clay slates on the west and greenstone on the east. On each side of the contact, for a limited distance, the rocks are more or less mineralized with gold, and hence we have, in many cases, a series of more or less parallel locations indicating the points at which the quartz segregations have shown themselves on the surface. When the line of contact is more nearly vertical, the quartz bodies seem to be more solidly compacted and continuous; when it is flatter they seem to be more disseminated through the lateral country rock. Usually there is quartz on the line of contact, and one or more bodies between the hanging and foot-walls.

AMADOR COUNTY.

This county is about fifty-five miles long, with an average width of twelve miles, and although it has less area than most of the other mining counties of the State, it ranks, at present, among the foremost in production of gold. It is bounded on the north by El Dorado County, and by Calaveras on the south, and through its central portion, in a northwesterly and a southeasterly direction, runs the mother lode. East of the mother lode there is a belt of limestone, entering from Calaveras County, passing Volcano and extending toward the Sierras. The formation in the southern part of the county is of a volcanic origin, whilst in the northern portion are the gold-bearing slates.

Throughout the whole extent of the auriferous belts of the county there is an unusual amount of activity, and a decided feeling of contentment, not only in the present satisfactory production of the mines, but in expectation of an enlarged future yield. Properties abandoned in the years gone by, on account of the high price of labor, and the expense of motive power consuming the production, have recently been reopened, and, by the substitution of water for steam, are now in paying condition; again the developments in the new finds are very encouraging.

PLYMOUTH CONSOLIDATED.

As a dividend-paying property, this mine is not excelled by any other on the mother lode. The mine in altitude is 1,050 feet above sea level, has a length of 4,800 feet on the lode; both hanging and foot-walls are slate; the course of the vein is north and south, dips 55° to the east, and has an average width of 30 feet. There are two water power mills on the property of 80 and 40 stamps respectively. In the larger mill the stamps weigh

750 pounds each, whilst in the smaller, the weight of each stamp is 1,000 pounds; the fall of the stamps is 7 inches, at the rate of from 90 to 100 times per minute, crushing about two tons to the stamp every 24 hours. The method of recovering the free gold is by amalgamation in the batteries and collection on the outside plates; the sulphurets are collected on Frue concentrators, and worked by the chlorination process, at the company's works, at an expense of $10 per ton.

The following is the last quarterly report of the company:

The dividend paid on October fifth by the company, was the forty-first consecutive monthly dividend, making a total of $1,775,000. It is stated that the mine has more ore developed than at any previous period in its history. At present the mills are supplied with low grade rock from the upper levels. No stoping has been done in the bottom, the ore there being reserved for future use. The entire plant, including mills, shops, etc., is in perfect running order. Level No. 6 (1,500 feet) has been opened one quarter of its length, and promises to be the best in the mine. Large masses of low grade rock have been uncovered between the 800 and 900 levels, and a new ore body is now being worked on the 800. Its full size is unknown, but appearances indicate an extensive deposit.

Is situated at the southeast end of the town of Amador, about two miles northwesterly from Sutter Creek, in the Amador Mining District, and has an altitude of 1,000 feet above sea level. The consolidation includes Spring Hill, Geneva, and Garfield claims. The location was made in 1850, and has since been worked almost continuously. The eastern, or hanging wall, is a metamorphic rock called by the miners greenstone, but so far the foot or western wall is not well defined. Lying against and on the west side of the greenstone is a large vein of low grade quartz; thence westerly there are from 200 to 300 feet of argillaceous slate in which the best ore deposits

occur, thence an admixture of slate and spar in which ore does not exist. The average width of the zone is about 400 feet; the course of the vein is northwesterly and southeasterly. The hanging-wall dips easterly at an angle from 45° to 60° at the surface, and 45° at the bottom; length of the shoot is 800 feet. There are two shafts north and south; the north shaft, used for hoisting the ore from the mine, is 1,305 feet on the incline of 49°, reaching a vertical depth of 1,000 feet; the south shaft, used exclusively for pumping out the water, is 1,125 feet on an incline of from 42° to 55°, with a vertical depth of 780 feet. The nature of the ores is free milling, carrying from one and one half to one and three quarters per cent of auriferous sulphurets. The method of reduction is crushing by stamps, and of recovery is amalgamating in the battery and collecting on copper plates on the outside. On the east side of the contact is a large, poor vein of quartz, varying in thickness from 2 feet to 40 feet, which is very spotted; 200 feet west from the greenstone, in the argillaceous slates, occur the next deposits, which are irregular and confined to a northwest and southeast channel; these deposits are from 2 feet to 30 feet thick, and a better quality of ore than that which is found on the east side. The west channel is from 300 feet to 500 feet west of the greenstone, from 3 feet to 40 feet in ore of the best quality found in the mine, paying as high as $40 per ton.

The sulphurets are iron pyrites combined with a small percentage of arsenical and antimonial sulphurets, and have an assay value of $110 per ton. The method of saving the sulphurets is by Hendy concentrators, riffles, and blanket sluices, and the gold is extracted therefrom at a cost of $20 per ton to the company at the chlorination and leaching works of Barney & Voorhies, Sutter Creek.

The mill is run by water-power; contains 40 stamps of 750 pounds each, with a drop of from 7 to 8 inches, 96 times per minute, crushing 2 tons to the stamp in 24 hours. The batteries are both high and low discharge, with number 8 slot screens; the apron plates are 16x14 inches, and sluice plates 14 inches wide. The total length of the plates for the 40 stamps is 80 feet, with an inclination of 3 inches in 10 feet. The amount of water used in 24 hours, in mill, is 125 inches, with a pressure of 254 feet.