Publisher's Synopsis
Excerpt from Gold and Silver Mining as a Geographic Factor in the Development of the United States: A Thesis Presented to the Faculty of the Graduate School of Cornell University for the Degree of Doctor of Philosophy
In the early days of quartz-mining the ore was crushed by stamps or rollers, and the rock our washed as in the placer works. This pro cess in its most perfect state did not save all the gold, so others were devised to meet the di cult combinations presented by the ores. A method known as the chlorination process has now come to be used extensively. The crushed ore before or after concentration, and some times after roasting, is treated with chlorine gas, which forms chloride of gold, soluble in water and removed by washing. From this solution the gold is easily recovered by precipitation with iron sulphate. Stamp mills customarily accompany chlorination plants, and smelting works are some times associated to handle special ores. This process is especially adapted to rather high-grade ores and those practically free from iron. A second chemical method probably more used than the above is known as the cyanide process, and is most serviceable in the treatment of low-grade ores. It finds its special field in the reduction of ore carrying iron and copper sulphides. The crushed ore in a slime condition is treated with a strong solution of potassium cyanide, usually strongly aerated, and the gold is thus brought into solution and separated from its refractory native compounds. Furnaces Often follow the cyanide tanks, where with suitable uxes the reduction to metallic gold of specially rebellious ores, by means of chemical reactions requiring heat, is effected. Had the ore occurred in small or more scattered deposits, even these processes would probably fail to extract the metal economically; but since large quantities of ore, even though of low grade, can be obtained within a limited area and be treated simultaneously, the expensive plant with its trained men, technical skill, valuable apparatus, altogether a costly equipment, can be Operated at a profit. Illustrations of the failure of extensive plants to remain in operation are common and usually they go out of business because the deposits are not as large as supposed, or because their contents are found to change character in the course of development, or because. Some resource, water, fuel or timber, has failed.
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