Silver ore

“ We come next to speak of silver ore, another egregious folly of mankind. Silver is never found but in shafts sunk deep in the ground, there being no indications on the surface to raise hopes of its existence, no shining sparkles, as in the case of gold. The earth in which it is found is sometimes red, sometimes of an ashy hue. It is impossible, too, to melt it, except in combination with lead or galena, the latter being the name given to the vein of lead that is mostly found running near the veins of the silver ore. ”

“ Gold is always found as a metal, never as an ore, and the separation from the accompanying vein-stone with which it is mixed mechanically, is much more simple and easy than the reduction of the argentiferous ores in which the silver is chemically combined with base substances, for which it has a strong affinity. Chemical knowledge and chemical processes are more necessary in mining for silver than for gold; and while all auriferous quartz is of the same kind, and may be treated in the same manner, there are many different kinds of silver ores, each of which requires a peculiar treatment. ”

“ Assay of Silver Ore.—Pure silver is easily recognized. But lead and copper ores often contain a large percentage of the precious metal.
To detect silver in lead ore, dissolve the powdered ore in strong nitric acid; pour off the liquid and insert a piece of pure copper. If silver is present, it will go to the bottom. Or, add to the liquid a solution of common salt, and it will instantly become cloudy or white. If lead ore yields three ounces of silver to a ton, it may be worked for the silver as well as the lead. In Colorado, the average value of silver-bearing galena is $100 per ton. ”

“ Strictly speaking, silver mining does not exist as a distinct operation in Great Britain, for it can hardly be said that this country possesses any great quantity of silver ore. Yet we must not disguise or leave unnoticed, in dealing with this subject, the positive fact that silver is found to some extent in our copper and lead mines, principally in the latter; but in no case, as far as we know, have mines been worked for the sake of the silver alone. It is almost always found in conjunction with lead, and it is from that source that we have a good supply of British silver. ”

“ It requires very good judgment to determine just how much foreign material and lime is needed to produce the best results with the constantly varying ores. Luck may find the silver ore but science must extract the bullion. Most profit accrues to the smelter when the ore produces from seventy-five to two hundred ounces of silver, and contains a goodly proportion of iron and lead. ”

“ Most silver ores are easily recognisable, and readily tested by means of the blowpipe or simple fire assay. Sometimes the silver on being tested is found to contain a considerable percentage of gold, as in the great Comstock lode in Nevada. Ore from the big Broken Hill silver lode, New South Wales, also contains an appreciable quantity of the more precious metal. A natural alloy of gold, termed electrum, contains 20 per cent. ”

“ The entire product of the United States was 300 ounces in 1898; valued at $3,837. In 1899 there was none produced.
Silver. Silver is generally found in serpentine, trap, sandstone, limestone, shale, or porphyry rocks, the gangue being quartz, calc, fluor, or heavy spar. All silver ores are heavy, and many of them are sectile, i.e., may be cut with the knife. Western men test for silver by heating the ore and dipping it into water. Some metal comes to the surface in a greasy scum, should silver be present. Native silver is found occasionally. ”

“ Though the original condition of the ore was doubtless sulphide, it now contains, as the result of oxidation, hematite, limonite, magnetite, malachite, azurite, chrysocolla, cerussite, wulfenite, chloride of silver, manganese oxide, and metallic gold. The value of the ore lies principally in the gold contained, though in one portion of the ore body, near its eastern end, rich chloride of silver ore is found, with but little gold. The physical appearance of the ore is no criterion of its gold contents, as two pieces, with identically the same characteristics, will differ widely in value. ”

“ They are interspersed with veins of gold and of silver ore, in which pieces of pure silver, solid copper, and lead ore occur, frequently intermixed with white silver ore, and virgin silver, in threads. ”

“ Silver, is found particularly in veins and beds, in primitive and transition formations; though some veins of this metal occur in secondary strata. The rocks richest in it are, gneiss, mica-slate, clay-slate, greywacke, and old alpine limestone. Localities of silver-ore itself are not numerous, at least in Europe, among secondary formations; but it occurs in combination with the ores of copper or of lead. ”

“ Sometimes quartz, schist, or marble is of this quality also, if much native or rudis silver adheres to it. But that ore is considered of poor quality if three librae of silver at the utmost are found in each one hundred librae of it [9] . Silver ore usually contains a greater quantity than this, because Nature bestows quantity in place of quality; such ore is mixed with all kinds of earth and stone compounds, except the various kinds of rudis silver; especially with pyrites, cadmia metallica fossilis, galena, stibium, and others. ”

“ Since then development has considerably increased these reserves. In addition there is estimated to be 1,600,000 tons of low-grade ore averaging 5.1 ounces of silver, 7.5 per cent. lead, 4.8 per cent. zinc, and 0.2 per cent. copper per ton, with excellent prospects of larger developments. A large tonnage of gossan outcrop ore containing 4 or 5 ounces silver, 4 to 5 per cent. lead, and a little zinc is cheaply mined and available as siliceous flux. The essential constituents of the ores are galena and sphalerite with a little pyrite and chalcopyrite. All of the ore is argentiferous. ”

“ Like that of gold, the first discovery of silver precedes the historic times, and must no doubt be sought for in the remotest antiquity; for as it is not seldom found in a native state, its brilliancy could not fail to attract attention at a very early age. Veins of silver ore, moreover, not seldom crop out on the surface, a circumstance which likewise greatly facilitated the accidental discovery of the metal. ”

“ They are also harder to melt; and the lead obtained is not of so soft and malleable a nature as that procured from the broad-grained, easy-melting ore.
The proportion of silver in lead varies greatly. It is sometimes found to yield as high as twelve per cent., and is then called argentiferous lead-glance; but, in the poorest ores, it does not yield more than one ounce out of three hundred. To separate the silver from the lead, a process is pursued called the refining of lead, or cupellation. ”

“ They are working upward from the floor of the level, and as they progress they build up square sets of supporting timbers in the cavities or chambers cut out in extracting the ore from the bonanza. Even here, well toward its south end—as far as explored—the ore-body is by no means small, being over nine and one half rods in width! This is not a mixture of ore and worthless rock, but is a solid mass of rich silver-ore which is sent to the mills just as it is dug or blasted down—ore that will pay from $100 to $300 per ton. ”

“ Occurs in crystals, wax-like masses, or in crusts; when scratched shows a shining streak; becomes brown on exposure; quite soft, easily cut; a small piece placed on zinc and moistened, swells up, turns black and shows metallic silver on being pressed with a knife; dissolves in hartshorn; gravity 5.5.
Value.—An ore of silver, yielding seventy per cent.
Localities.-Found in slate with other silver ores. Lake Superior Mining Region; Austin and Comstock Lode, Nev.; Willow Springs and San Francisco districts, Eldorado Cañon, Ariz. ”

“ A distinguished American chemist said not long ago that he would like to extract all the silver from a large body of lead ore in which it occurs so commonly, and then come back after twenty years and look for further traces of silver, for he felt sure that they would be found and that lead ore is probably always producing silver in small quantities and copper ore is producing gold. ”

“ You have been here in Silverland—here in Nevada—two or three years, and, of course, your position on the daily press has made it necessary for you to go down in the mines and examine them carefully in detail, and therefore you know all about the silver-mining business. Now, what I want to get at is—is, well, the way the deposits of ore are made, you know. For instance. Now, as I understand it, the vein which contains the silver is sandwiched in between casings of granite, and runs along the ground, and sticks up like a curb-stone. ”

“ As the silver necessarily increases in the hearth, it will require to be occasionally withdrawn, in order to make room for a further supply of lead ore. This process is adopted when it reaches about from 8 to 10 per cent. of silver to the ton (between 2,000 and 3,000 ozs.) , and may be effectually performed by drilling a hole underneath the cupel, and letting the silver flow through it into a receptacle placed to receive it. Of course the operations of the furnace are arrested while these manipulations are being carried on. ”

“ With increasing depth the amount of galena and zinc blende gradually increases, until at a depth not exceeding 100 ft. they decidedly predominate. The principal silver-producing county is Clear Creek. The actual development of the prominent silver lodes was begun in 1867; the whole amount of ore mined up to April 1, 1869, is estimated at 1,100 tons, which yielded $250,000 in coin. The production of silver ore in Clear Creek county amounts to about 2,000 tons per annum. The estimated yield of silver, including shipments of ore, during 1870, was about $400,000. ”

“ The assay reported for the Daisy ore [Pg 166] gives silver 50 ounces, gold $2.00, lead 30 per cent., and iron 25 per cent. It is self-fluxing.
Young America Company.Sixteen miles and a half northward from Colville, near the Columbia River, a rich discovery of silver-lead ore has been made by the Young America Consolidated Company. The vein averages five feet, runs northeast and southwest, and has been shafted through ore to the depth of 180 feet. A test showed 90 ounces of silver and 40 per cent. ”

“ Native and massive silver is, however, necessarily rare, and only occurs in small and scattered portions among other metals of good quality. The better the quality of the ore, so much greater is the damage and loss from robbery sustained by the mine and master miner; and it often happens that the cost of raising the ore, extracting the silver, paying government and local duties, the repair of the underground works, supply of salt and quicksilver, together with all the expense of major-domos, and wear and tear of [14] mining utensils, loss on cargo-mules and llamas, &c. ”

“ The silver produced in Great Britain is extracted from an argentiferous lead, to the amount of 550,000 to 700,000 oz. annually (in 1872, 628,000 oz.) . The celebrated Kongsberg mines in Norway, discovered in 1623, have been worked almost continually since. The ore occurs in parallel belts of rock, intercalated in gneiss and crystalline schists, and impregnated with sulphides of iron, copper, zinc, and sometimes lead, cobalt, and silver. Fissure veins traverse these belts occasionally, and are argentiferous at the intersection only. Beautiful specimens of native silver occur. ”

“ We are informed that a mass of capillary native silver was found, in veins traversing the blue-coloured limestone of Isla, one of the Western Islands of Scotland. Great quantities of silver are extracted from lead. There was lately melted in one refining house in London 50,000l. worth of this metal, from lead of the Beralston mines in Devonshire.
Different methods are employed, in different countries, to extract silver from its ore. In Mexico and Peru the mineral is pounded, roasted, washed, and then mixed with mercury in vessels filled with water ”

“ Even had a more suitable treatment plant been provided it is almost certain that such silver values as there were in the ore would not have proved payable, but there is a possibility that if the company had given attention to the recovery of the gold rather then the silver contents of the ore it might have met with a greater measure of success. ”

“ Oxides of silver are also common in some of the silver mines in Germany. Silver has lately been found in a copper-mine in Cornwall.106 Most of our lead mines also afford it, particularly some in Scotland. In the county of Antrim, in Ireland, there is a mine so rich, that every thirty pounds of lead ore is said to produce one pound of silver. ”

“ The rarity of iron during the primitive periods arises chiefly from the occurrence of the ore in a form least resembling metal, and requiring the most laborious and difficult processes to reduce it to a state fit for use; while the absence of silver is no less satisfactorily accounted for from the mining operations requisite for reaching the argentiferous veins, which were only possible when the introduction of the more useful metals had supplied an abundance of the requisite tools. ”

“ This produce is most extraordinarily large, being equal to four parts of pure silver from ten of ore, or 640 ounces of silver from the quintal or 1600 ounces of ore. At the present time, the silver mines in Mexico, which are the most productive of any that have ever been known, are remarkable for the poverty of the mineral they contain. A quintal or 1600 ounces of ore affording only at an average 3 or 4 ounces of pure silver. ”