USA > California > Nevada County > Bean's history and directory of Nevada County, California. Containing a complete history of the county, with sketches of the various towns and mining camps also, full statistics of mining and all other industrial resources > Part 27
Note: The text from this book was generated using artificial intelligence so there may be some errors. The full pages can be found on Archive.org (link on the Part 1 page).
Part 1 | Part 2 | Part 3 | Part 4 | Part 5 | Part 6 | Part 7 | Part 8 | Part 9 | Part 10 | Part 11 | Part 12 | Part 13 | Part 14 | Part 15 | Part 16 | Part 17 | Part 18 | Part 19 | Part 20 | Part 21 | Part 22 | Part 23 | Part 24 | Part 25 | Part 26 | Part 27 | Part 28 | Part 29 | Part 30 | Part 31 | Part 32 | Part 33 | Part 34 | Part 35 | Part 36 | Part 37 | Part 38 | Part 39 | Part 40 | Part 41 | Part 42 | Part 43 | Part 44 | Part 45
The gold in many of the Grass Valley mines is very easily worked, being clean, an- gular and not very small, hence it is readily entangled in the fibre of blankets, together with a considerable portion of sulphurets, naturally leading to the method most commonly in use in Grass Valley for treatment of the gold ores.
The Grass Valley Method of Amalgamation,-What may properly be called the " Grass Valley mode" consists in the use of heavy stamps, seven hundred or a thousand pounds, crushing usually two tons, sometimes two and a half tons of ore each in twenty-four hours-through screens not exceeding No. 6, rarely so fine. Amalgamating in battery and copper aprons are usually united. In some mills, murcurial riffles are placed in front of the discharge, but more commonly the whole body of crushed stuff is led at once over blankets, which are washed out every few minutes into tanks where the free gold and sulphurets are allowed to collect pre- paratory to being passed through the " Attwood amalgamators." These simple
B. GAD'S IS THE PLACE TO FIT YOURSELF WITH FINE CLOTHING.
DIXON'S VARIETY STORE, NO. 4, MILL ST
GRASS VALLEY TOWNSHIP DIRECTORY.
2.37
machines are designed to bring the gold into thorough contact with murcury con- tained in little vats sunk in the surface of an inclined table, over which the stuff is fed to the vats in a regulated manner by a stream of water, while iron blades slowly revolve in the vats to cause a mixture of the sands and quicksilver. By this apparatus, at thy Eureka mill ninety per cent. of all the gold is obtained which is saved from the dre. Beyond the amalgamators, the sands are carried over amal- gamatic copper sluices, and are put through various ore-saving processes with a view especially to concentrating the sulphurets. These processes vary much in different mines. In some mills, especially the Ophir, much more elaborate me- chanical apparatus has lately been introduced-with what results still remains to be seen. It is certain that if the method of treatment just sketched seems imper- fect, (as it undoubtedly is,) it is the method which has hitherto yielded the large returns of gold for which Grass Valley has obtained its well-deserved renown. As the development of the district goes forward, cases will occur of veins containing gold in a state of very fine division, to which other methods of treatment must be applied. Such examples indeed already exist, and the problems which they offer will be met by the use of other systems of amalgamation-or by suitable modifica- tions of the existing system.
Value of the Sulphurets .- The sulphurets occurring in the Grass Valley District are usually rich in gold-some of them remarkably so. In quantity they probably do not on an average amount to over one per cent. of the mass of the ores, although in certain mines they are found more abundantly. For a long time there was no better mode known of treating them than the wasteful one of grinding them in pans and amalgamating. In this way rarely was sixty per cent. of the gold tenor saved. After many abortive efforts, at length complete success has been met with in the use of Plattner's chlorination process. Mr. Deetken, now connected with the reduction works of the Eureka mine, is entitled to the credit of having over_ come the difficulties which formerly prevented the successful use of this process in Grass Valley, a more detailed description of which will be found in our notice of the Eureka minc.
Length aud Depth of Productive Ore Ground .- Of the length of the productive portion of quartz veins and the depth at which they commence to become produc- tive, Grass Valley offers some instructive examples :
The North Star vein, on Weimar Hill, has been proved productive on a stretch of about one thousand feet, while the tenor of gold has gradually increased with the depth, from an average of twenty dollars in the upper levels to nearly double that in the lower levels. The limits named are rather those of exploration than the known extent of the productive ore. In the vein on Massachusetts and Gold Hills, on the contrary, the distribution of the " pay " has been found much more capricious, being at times extremely rich and again with no apparent reason yield- ing scarcely the cost of milling. The Eureka mine offers the most remarkable example, however, of a steady increase from a non-paying tenor of gold near the outcrop to one of uncommon productiveness. An opinion has found advocates, and has been perhaps generally accepted by most writers on the subject of gold-bearing quartz veins, that they were richest ncar surface and in depth became gradually poorer. There is nothing in the nature of the case, as it seems to me, to justify such a generalization, more than there is to sustain an opposite opinion. If we
BOYS SUITS, AND UNDER-CLOTHING, ALL SIZES, AT B. GAD'S.
PORTFOLIOS, AT DIXON'S.
238
GRASS VALLEY TOWNSHIP DIRECTORY.
accept facts as a guide, we find in California that the deepest mines, for example, Hayward's Eureka, in Amador, 1,200 feet, North Star, 750 feet on the slope, Princeton, in Mariposa county, 800 feet, Eureka (Grass Valley) 400 feet, Allison Ranch, 525 feet, etc., as a rule have had an increasing tenor of gold. If the Allison Ranch, the Princeton mine, and some others appear to be exceptions, the answer is, we may reasonably expect the same variations of productiveness in depth which are known to exist in linear extent. The Princeton, after an excellent run of good ore, be- came suddenly poor, at a depth of over six hundred feet, in 1865 ; but I am informed by Mr. Hall, the present superintendent, that the good ore came in again in a short distance. Mr. Laur, the Frenchi engineer, whose papers of California mines is often quoted, cites the Allison Ranch mine in evidence of the theory of a decreasing tenor of gold in depth, but it is in proof that since the date of Mr. Laur's visit (1862-3), this mine has been at work on ores which have yielded over one hundred dollars value, its present suspended activity being due to causes quite unconnected with the intrinsic value of the mine. The rich " chimneys," or productive zones of ore ground, are known to be of various extent in quartz veins, from a few feet to many hundreds of feet, and it is impossible to assign any valid reason why we may not expect the same changes in a vertical direction which we find in a horizontal. As the ore-bearing ground or shoots of ore have in many, if not in most cases, a well-determined pitch off the vertical, it is self-evident that a vertical shaft, or in- cline at right angles to the vein must, in descending, pass out of the rich into poor ground, at certain intervals, and it is perhaps due to an ignorance of this fact that miners have abandoned sinking because they found the "pay " suddenly cease in depth, when a short distance more would probably bring them into another zone of good ore. The experience of every gold mining district offers examples in illus. tration of these remarks. In quartz veins containing a considerable amount of sulphurets, it is evident that the out-croppings should offer much better returns to mining industry than will follow after the line of atmospheric decomposition has been passed, because above this line nature has set free the gold formerly en- tangled in the sulphurets, leaving it available for the common modes of treat- ment, with the added advantage often times that the particles of free gold formerly distributed through a considerable section of the vein, are found concentrated in a limited amount of ore. It is easy to reach the conclusion in such cases, that the tenor of gold in the vein is less in depth, after the real average tenor is reached, while in fact it is neither greater nor less ; but the metal is no longer available by common methods of treatment.
Not wishing to extend these general considerations to an undue length, let us turn our attention to a very limited number of the most characteristic and successful Grass Valley mines. It will not be considered invidious if we confine our attention specially to the Eureka, North Star and Allison Ranch mines, acknowledged by all to be, at present, perhaps the most important mines in this district. Massachusetts Hill rests on its past history, but it is is to be hoped that all the separate owner- ships on that hill may at no distant day be consolidated, when systematic work with reference to the best exploration of the whole lode can be resumed with the expectation that it may again become as productive as in former years. The mines of the Ophir Company are also worthy of honorable mention, and are said to be rapidly coming to the front rank.
WHO KEEPS THE GREAT CLOTHING EMPORIUM, CORNER OF
239
PARLOR GAMES, FULL SUPPLY AT DIXON'S.
GRASS VALLEY TOWNSHIP DIRECTORY.
The Eureka Mine.
Historical .- From the date of its location, February 7, 1857, to the close of 1858, this mine proved only a source of expense to its owners, and its history is instruc- tive as suggesting that shallow surface explorations, in gold mining, may be as unsatisfactory as they are known to be in other mining enterprises. So late as 1858, it is said, that five thousand tons of quartz taken from above the drain level, or thirty feet from the surface, yielded in mill less than ten dollars per ton in gold, not returning expenses. A shaft sunk to a depth of about fifty feet afforded quartz, however, which yielded about fifteen dollars per ton, and its tenor of gold rapidly increased to twenty-eight dollars at one hundred feet. Between the one hundred andl two hundred feet levels the average yield was about thirty-seven dol- lars per ton, and between the two hundred and three hundred feet levels the aver- age has been abont fifty dollars per ton, rising to sixty-four dollars in the last four months of 1866.
Description of the Mine .- This mine is distant about one and a fourth miles from the town of Grass Valley, and is opened on a vein which runs nearly east and west, dipping south at an angle of about seventy-eight degrees. The vein varies from a few inches in thickness to nearly six feet, and over the whole extent of some seven hundred feet which has been worked the average is nearly three feet. It is opened by a vertical shaft which cuts the vein at three hundred and seventeen feet from surface, and then follows the pitch of the vein to the fourth level four hun- dred feet from surface. There is a ladder way, independent of the shaft, following the inclination of the vein, for the use of the miners in ascending and descending the mine. A new shaft, five by twenty feet, is now being raised from the third level to surface, on the slope of the vein, and one hundred and seventy feet west of the hoist- ing shaft, designed to explore the mine to a great depth. It will have four com- partments-one for pumps and pit work, one for a bucket and two for safety cages, adapted to hoisting tram wagons of ore, and for the accommodation of the miners in reaching and ascending from their work. All the hoist-ways will be actuated by a powerful hoisting engine, with reels and flat steel ropes for the cages, making it the most completely furnished mine in the gold regions of California. The mine is not wet, nearly all the water coming in at the upper levels, while in the lowest level no pump has yet been required. This new shaft, it is expected, will be ready for work in the autumn of this year (1867), after which more active explo- rations, both in depth and extent, will be possible than the present limited hoist- ing capacity of the mine will permit.
Nature of the Vein .- There are in fact two distinct veins in the Eureka mine, separated from each other by a mass of greenstone or metamorphic sandstone, about twenty-eight or thirty feet in thickness. The smaller of these veins is on the South and has not been explored, but is a well-defined vein at the points where the shaft and cross ents have exposed it. The greenstone forms the hanging wall of the main vein, and is particularly regular and smooth, in some places beautifully pol- ished. The foot wall consists in some parts of soft serpentine, and when the vein pinches it appears to be from swelling of the foot wall. No other mine in this region has such a structure as the Eureka, so far as I know, and there is very much in the peculiarities here described to favor the highest confidence in the perma- nence of this great ore channel, both in depth and extent.
MAIN AND MILL STREETS, GRASS VALLEY ? B. GAD.
BLANK BOOKS, FULL SUPPLY AT DIXON'S,
240
GRASS VALLEY TOWNSHIP DIRECTORY.
Extent of Exploration .- The extent of exploration on the three hundred and sev- enteen feet level is over eight hundred and thirty feet, viz : west of the hoisting shaft three hundred and eighty-five feet, and east of the same point four hundred and forty-seven feet, and the ore still holds good. The whole of this distance was not found equally productive, being divided into two main ore bodies or chimneys, with about one hundred and twenty feet of ground between them, with a tenor of gold of about twenty dollars to the ton. Near both the three hundred and seven- teen and four hundred feet levels a "horse" of slate or greenstone, ("cab" of the miners,) was found in the body of the vein splitting it into two parts, but of limited extent. The vein stone carries, as its characteristic feature, seams of slate matter, giving a structure somewhat laminated, the mass splitting more easily in these lines. The sulphurets of iron, copper and lead, which are found in the Eureka vein, are also often arranged in ribbon-like order, and form probably about two per cent. of its mass. The amount actually saved by concentration from the tail- ings and in milling, is about one and one-fourth of the whole mass worked.
Product of the Mine Under Present Ownership .- Early in October, 1865, Messrs. Fricot & Co., the former owners, sold the Eureka mine to its present owners for $400,000, which sum was increused to about $500,000 by subsequent purchases. The property is held in twenty shares, the market value of which has steadily in- creased under the able administration of the Messrs. Watt Brothers, in whose hands all details of management have been wisely left.
By the books of Messrs. Hentsch & Berton, the bankers of the Eureka mine, I find the bullion received by them from this mine, from October 25, 1865, to April 17, 1867, amounted to $825,936 15, to which properly belongs the value of a cer- tain accumulation of sulphurets, still on hand, estimated to be worth'in round numbers $10,000 ; and the month of April being estimated at a total of $50,000, we shall have the grand total in round numbers, for nineteen months, of $885,000. Deducting the month of October, 1865, when but little work was done, we find the monthly average for the eighteen months, to May 2d, to be $47,000 ; the largest monthly return in any one month being in June, 1866, $65,841 39, without the sulphurets, which would make the aggregate for that month over $70,000. The monthly expenses have averaged about $16,000, including all costs of machinery, supplies, and permanent improvements.
Progressive Increase in Gold Yield .- It is interesting to analyze a little more in detail the returns of this mine, as illustrating a point already alluded to, viz-its progressive inerease of gold tenor with an increase of depth.
From October, 1865, to December 31, 1865, the quantity of quartz erushed was twenty-four hundred and forty-five tons, yielding an average of $33 87 per ton, and costing to mine and reduce $13 51.
From January 1st to June 1, 1866, the crushing was forty-seven hundred and three tons, averaging $42 67 per ton, at a cost of $12 52 per ton.
From June 1st to September 30, 1866, the amount of quartz crushed was forty- two hundred twenty-seven and three-fourths tons, giving an average yield of $60 33 per ton, at a cost of $15 78 per ton.
For the whole year ending September 30, 1866, the total erushing was eleven thousand, three hundred and seventy-five and three-fourths tons, yielding a general average per ton of $47 15, at a mean cost per ton of $13 75.
B. GAD ALWAYS KEEPS THE BEST BOOTS AND SHOES.
GUITAR AND VIOLIN STRINGS AT DIXON'S.
241
GRASS VALLEY TOWNSHIP DIRECTORY.
The net profits for the year ending September 30, 1866, were $368,042 18. The ratio of costs of mining to the gross product was, for the three periods named above, respectively, 40}, 20} and 26} per centum. In the mining costs are included all charges for dead work, machinery, etc. The profits of the Eureka mine have, therefore, for the period named, averaged in round numbers from sixty to seventy- four per cent. of the gross product of the mine. The earnings of the mine are di- vided every twenty-eight days, making thirteen annual dividends.
The bullion of the Eureka mine is about 850-thousandths fine, worth $17 57 per ounce. This value is, of course, slightly variable, say within five-thousandths.
The Eureka Mill.
The mill on the Eureka mine was built by Fricot & Co., in 1864, at a cost of about $20,000. It has twenty stamps, weighing eight hundred and fifty pounds cach, and making sixty blows each minute, crushing two tons daily to each stamp, or abont one thousand tons of quartz per month. The mill is driven by an engine of sufficient power to carry forty stamps. The mortars weigh forty-five hundred pounds each, and are provided with a frame for holding the screens in place, the invention of Mr. W. W. Boston, the engineer and designer of the mill.
Amalgamation .- The system of amalgamation in use at the Eureka mine has al- ready been sketched in its main features. The screens used on the batteries are, if of perforated iron, number five, giving one hundred and forty-four holes to the square inch. If brass wire cloth is employed, it is number forty mesh, giving 1,600 openings to the square inch. As no mercury is used in the batteries wire cloth may be, and is often employed with advantage. Two stamps deliver to one apron, with a supplemental one to aid in changing the blankets, which are constantly. washed out into tanks to collect the sulphurets and free gold caught by the blank- ets. The blanket sands are found to contain ninety per cent. of all the gold which is saved by the mill. These sands are treated in three of Atwood's amalgamators, and the " skimmings " from these are ground in two of Knox's pans. The sands from the amalgamators are passed over Hunter's Eureka Rubber, a table provided with oscillating rubbers suspended over an amalgamated copper surface, and with mercurial riffles, and designed to catch particles of amalgam that might otherwise escape. These machines effect a small additional saving of gold, and are approved by Mr. Watt. The muddy water, from all sources, runs over a considerable extent of copper plates amalgamated. The labor required to manage this mill is, for each period of twenty-four hours, as follows : Rock-breakers, four ; feeders of stamps, four ; washers of blankets, four ; engineers, two ; amalgamator, one. Total, nine- teen men.
Sulphurets .- The sulphurets are concentrated chiefly by hand, with rockers and sluices, and after the mine abandons them are worked on shares by ore dressers or tributers, who employ chiefly the Cornish methods.
The treatment of the sulphurets has been attended with better results at this mine than at any other in California, so far as I am informed, by the use of Platt- ner's chlorination process. This department is under the direction of Mr. G. F. Deetken, who has introduced important improvements in its management, enabling him to obtain results very closely approaching the actual value of gold present.
Plattner's Process .- This process depends on the fact that metallic gold is dis-
D2
B, GAD ALWAYS KEEPS THE BEST BOOTS AND SHOES,
GIFT ANNUALS AT DIXON'S.
242
GRASS VALLEY TOWNSHIP DIRECTORY.
solved by moist chlorine gas, while the metallic oxides or chlorides with which it is associated in the roasted ore, are mostly unacted upon. In using this process, the concentrated sulphurets containing gold are first roasted " dead " on the hearth of a reverberatory furnace, which for a charge of one ton of sulphurets has an area of about one hundred and forty square feet, the dome rising about twenty-five inches over the hearth. The charge of sulphurets is delivered through an open- ing in the top of the dome, where a hopper receives them from a tram wagon. From the time of charging to the completion of the roasting and the arrival of an- other charge on the hearth is twenty-four hours. The labor required is that of two roasters, or furnace men, one laborer to turn and handle the exhausted ores, and one superintendent. The materials consumed are, for each ton of ore roasted, ten pounds of manganese oxide, fourteen pounds of common salt, and the equiva- lent of sulphuric acid. The fuel required for roasting is from one cord or less of dry wood in dry weather to over two cords if the wood and atmosphere are damp. A small proportion of salt is used on the hearth with the roasting ore. A dust chamber is placed between the furnace hearth and the chimney to catch the parti- cles of ore carried over by the draft. The roasted charge is moistened after it is sufficiently cool, and is then transferred to a large wooden tub-shaped vat, capable of holding the product of roasting of three tous of sulphurets. This vessel is pro- vided with a false bottom leaving a small void space for the introduction of the gas. The roasted ore is supported on a bed of quartz sand, or tailings, and is sifted in gradually and evenly, care being had that it is neither too dry nor too moist. The gas is started as soon as a few inches of ore are in the vat, the ore being added as the gas follows, until the vessel is filled to within a few inches of the top, when a wooden top is luted on with flour paste or dough, and the dose of chlorine gas is kept up for about eight hours. Each ton of sulphurets yields about fourteen hun- dred and fifty pounds of the roasted ore. The chlorine is produced from the ac- tion of oil of vitriol (sulphuric acid) on common salt in presence of peroxide of manganese, in a leaden vessel set over a small furnace. This apparatus is provided with means of agitating the charge during the process, to avoid caking and the melting of the lead. The gas is carried by a lead pipe to an opening left in the lower part of the vat, being washed on its way by water. When the time men- tioned has expired, the vessel is permitted to remain until the next morning, when the cover being removed, spring water is suffered to pass through the mass of oxides as long as it washes out any chloride of gold. This solution is conducted to another wooden vat set at a lower level. The first solution which comes over is colored quite strongly yellow with chloride of gold. and so long as the solution, as tested from time to time with a solution of green vitriol, produces therewith the well known greenish-blue color and cloudiness of precipitated gold, the washing is continued. A freshly prepared solution of green vitriol-proto-sulphate of iron ---- is then permitted to flow into the lower vat until all the gold is precipitated, which settles as a snuff-brown powder on the bottom of the vat, and is finally col- lected on a paper filter and washed with water until all traces of the iron solution are washed out of it, when its color is blue black, giving an excellent illustration of the change of color in metals due to differences in their physical condition. It is then fused with borax, and gives an ingot of 992 to 9963-thousandths fine. A small trace of gold yet remains in the effete mass of metallic oxides, which is saved by causing this waste material to flow with a stream of water over an inclined plane
WHO KEEPS THE GREAT CLOTIIING EMPORIUM, CORNER OF
RUBBER NECK-TIES AT DIXON'S.
-
GRASS VALLEY TOWNSHIP DIRECTORY.
243
covered with mercurialized copper plates. The proportion thus saved is not over two dollars per ton of sulphids, and results from particles of gold having a sensible size and which the chlorine had not dissolved. The sulphids of the Eureka mine run from $250 to $425 per ton in gold. The silver, amounting to ten or twelve dollars per ton, is lost by the Plattner process, as it is in quantity too small to justify the use of strong brine to save it from the waste as might be done, if it were worth while.
The cost of the whole process, including the salary of the superintendent, does not exceed twenty dollars per ton of the sulphurets treated. With only a single furnace the chlorination at the Eureka mine is conducted but twice a weck, three days' roasting going into one day's chlorination. If the work was conducted on a somewhat larger scale the cost would be a little less. It is believed that the chlo- rinntion process as now conducted will prove of immense benefit to the gold mines of California, among which there are many having abundant auriferous sulphurets, from which only a very small proportion of the gold is saved by the mechanical methods commonly in use. Great credit is due to Mr. Deetken for his skill in bringing this process to its present perfection, a result which has cost much labor and a prolonged and varied experience.
Need help finding more records? Try our genealogical records directory which has more than 1 million sources to help you more easily locate the available records.