CHAPTER IX.

MINING AND METALLURGICAL PROCESSES.

Gold-Placer Mining-The Shallow Placers-River Mining-The Deep Placers-Tunnel Mining-Hydraulic Mining-Blue Gravel-The Great Blue Lead-White Cement-Quartz, or Vein Mining-Mining Operations-Milling Machinery and Processes-The Grass Valley System of Amalgamation - Amalgamation in Battery --The Mariposa Process-Concentration-Plattner's Chlorination Process.

Although California is by no means wanting in the variety of its metallic ores, yet the number of different metals which, either in the native state, or mineralized as ores, have hitherto been made the object of successful and profitable exploitation, is comparatively small, comprising only gold, mercury, copper, and silver. Platinum and iridosmine are also incidentally obtained in small quantities, associated with placer gold. Deposits of lead ore have been found, but as yet are undeveloped. Iron ores of very superior quality have been discovered at several localities in great quantity. Some of these deposits are in many respects favorably situated, and although their distance from market, and the high prices of labor, transportation, etc., have so far prevented their being advantageously worked, yet, with additional railroad facilities, and the introduction of cheaper labor, this useful metal will no doubt shortly be produced in California in ample supply for all home demands.

Among other metallic ores known to exist within the State, and which possess a greater or less prospective commercial value, are zinc, chromium, manganese, nickel, cobalt, arsenic, antimony, and tin.

Of the non-metallic mineral products already contributing to the wealth of the State, the coal of the Monte Diablo mines is of primary importance. Next to this is the borax of Clear Lake, to which may be added native sulphur, and common salt, obtained in considerable quantities--the latter, as yet, chiefly from the evaporation of sea water, although extensive deposits of it exist in the solid form at various

localities in the interior of the State. Asphaltum also, a product of the southern counties, is used extensively for paving and roofing purposes. Many other mineral substances occurring in California will become of value for various manufacturing and commercial purposes in the future, some of them even now being turned to profitable account. Though silver has been included in the list of its metallic products, California can by no means be called a silver producing State-the greater part of that shipped from San Francisco being furnished by the mines of the State of Nevada. True, silver mines are not uncommon in the southeastern part of the State, and some of them contain very rich ores. This is especially the case in Alpine, Mono and Inyo counties, lying east of the Sierras. Many attempts have been made to mine and work these ores; but the veins are usually small, and mining operations in these localities, under present conditions, can only be conducted at a heavy expense. Besides, these ores, though often rich, are generally among the more complex kinds, requiring peculiar treatment. Practical operations having, however, been mostly attempted by men possessing little or no acquaintance with metallurgy, have generally resulted in failure. Under more skillful management these mines could probably be worked with large and steady profits. The copper ores found in that part of the State bordering on Arizona are usually argentiferous, sometimes very highly so; and from these and other sources, California will ultimately, no doubt, become a large producer of silver. But at present most of the silver actually obtained in this State is derived by separation from the gold, which always contains more or less of it as an alloy-the amount procured from this source not being large. Thus, it will be seen, silver is not a leading, but rather an incidental product of California mining; and the metallurgical treatment of its ores, though of vital importance in the adjoining State of Nevada, is of little practical moment in California.

GOLD.

Among the mineral products of California, gold is incomparably the most important metal. Rapid and immense as has been the development of this branch of mining in California, it is yet, in view of future results, scarcely more than barely entered upon, the repositories of this form of wealth remaining comparatively intact. Gold, with rare exceptions, is found in the native or metallic state. It is never, however, perfectly pure, being always alloyed with more or less silver, and sometimes also with small quantities of platinum, copper, iron, mercury, palladium, iridium, rhodium, etc. It also occurs in a mineralized condition in

connection with other metals combined with tellurium. The minerals, sylvanite and nagyagite, are examples of this mode of occurrence; and other compounds of the same class, whose characteristics are as yet but imperfectly known, have been found at Carson Hill, in Calaveras county, at the Rawhide Ranch Mine in Tuolumne county, and at a few other localities in the State. But these telluric compounds of gold, though rich in this precious metal, are of rare occurrence, and possess no general interest. It has been a matter of doubt with some, whether the gold present in auriferous pyrites, mispickel, etc., existed in the metallic state or mineralized in combination with sulphur. The prevalent opinion among the best chemists being that in these ores the gold is always in the metallic state, though its mechanical subdivision is in this case almost chemically minute-it will here be assumed that such is the fact. The metallurgy of gold is thus entirely confined to the separation or extraction chiefly, though not entirely, by mechanical means, of the native metal from the earthy débris or the rocky gangue, which may accompany or contain it.

In the consideration of native gold, our attention is first drawn to the fact that it occurs extensively in two distinct and well characterized conditions. It is found either in the solid rock, usually in veins, whose gangue is almost universally quartz, accompanied by various metallic oxides and sulphurets; or else it is found in alluvial deposits, in the form of minute scales, pellets, coarser grains, or larger pieces, always more or less water worn, and mixed with the sand and gravelly débris of all sorts of rocks, whose degradation and comminution have been the slow work of ages preceding the advent of man. To the latter class of deposits the general name of placers has been given, and from these two prominent modes of occurrence have arisen two distinct modes of mining, viz: placer, and quartz, or vein mining.

PLACER MINING.

The placers themselves may be again subdivided into two prominent classes, the deep and the shallow; or, speaking generally, the ancient and the modern placers. In California, these deposits, particularly the shallow placers, are also frequently styled "diggings," and these have again been further characterized according to their topographical position, as river, gulch, bar, flat, bench, and hill diggings; while the deeper placers have been called hydraulic diggings, tunnel diggings, etc., according to their situation, and the means adopted for their exploitation. At first operations were almost entirely confined to the

shallow or surface diggings, which owe their origin in great measure to the denudation and degradation, by mountain streams, of the older and deeper detrital formations-enormous quantities of the earthy and lighter materials having been washed away, while the gold has been left in a concentrated form and in positions readily accessible to the miner. Many of these shallow diggings, exceedingly rich when first discovered, having long since become either exhausted or greatly impoverished, are now almost wholly abandoned to the Chinese.

The methods and implements employed in placer mining, and by means of which such immense quantities of the precious metal were once extracted, seem insignificant compared with those now in use. In all placer mining the gold is obtained by washing the auriferous gravel, the sand and earthy matter being carried off by a current of water, while the gold, owing to its vastly greater specific gravity, remains behind, and can then be collected by itself in the metallic state or amalgamated by means of mercury.

THE SHALLOW PLACERS.

The principal implements employed in shallow placer mining are the pick and shovel, horn spoon, pan, cradle or rocker, long tom, and the sluice. The horn spoon is made by a lateral section cut from the horn of an ox, which, being scraped thin, forms a sort of curved spoon, from one to two inches in depth, two to three inches in breadth, and six to ten inches long. This spoon is used exclusively for "prospecting purposes"—that is, for testing the richness of auriferous gravel or pulverized rock, by washing in it small quantities at a time. In its use some skill is required, especially when, as is often the case, the gold dust is very fine, to save and exhibit as nearly as possible the whole of the precious metal present. This spoon holds at most but two or three pounds of earth, and it might seem that tests so rudely made could be of little value. It is found, however, to answer this purpose better than might be expected; and it is surprizing how closely an experienced prospector will estimate the probable yield of rock or gravel, after having made a sufficient number of trials with it to enable him to approximate an average of the mass.

The pan in present use is usually stamped from thin sheet iron, possessing the advantages of lightness and strength, while at the same time it is not attacked by the mercury often used. In shape and size, this implement resembles an ordinary circular dairy pan, with a twelve or fourteen inch bottom, the chief difference consisting in its having a more flaring form. In using this pan, it is first filled with the aurifer

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