TREATMENT OF GOLD ORES.

Thames Guardian and Mining Record, Volume I, Issue 147, 29 March 1872, Page 3

TREATMENT OF GOLD ORES.

Mr I*. d’Hciirease, of New York Oily, contributes the subjoined paper on the professed improvement in the extraction of gold from its ores to the Scientific American :

The numerous discussions, on the imperfect manner in which quicksilver amalgamation performs the gold extraction of Colorado ores (and, for that matter of Californian and other gold ores in general), and the desire to discover means by which the amalgamation may be improved, are hut another illustration of the observation, frequently noticed in your pages of late, that the human mind is apt to follow a well worn track, from which few only deviate. Amalgamation and concentration of the ores lias been practised with gold ores for centuries, and it is erroneously taken for granted that these two modes should form the basis of operations, which ingenuity is taxed to improve. It lias been shown that amalgamation, by the indifferent affinity of quicksilver for gold, secures on average, only a little over, if at all, one-half of the gold contained in the ore. It is also proved that in the process of concentration the fine particles of gold, flattened out exceedingly thin in the act of crushing the ores, are carried off in a large proportion as float gold by the stream of water used in concentration, as well as in battery amalgamation, and a proportion sometimes approaching nearly that secured by amalgamation ; for a float loss of lOdollarslo 15 dollars per ton in ores yielding but 10 dollars to 25 dollars per ton is by no means rare. This demonstrates, as it has done many years ago to this writer, a California miner of 1841), that we have to look for other means to avoid these losses.

Of all substances known, zinc, in a melted state, has the greatest affinity for gold (and silver) ; instant contact sufliccs to dissolve even heavy particles of gold by forming an alloy. Zinc does not combine directly with sulphur, but gold particles, covered with gold sulphurct and inert to the action of quicksilver, yield instantly to the zinc, as anybody can easily convince himself. The ore pulverised dry, and the dry (or dried) ore or tailings passed gradually through a hath of melted zinc, yields up, on an average, 80 to 90 per cent, of its auriferous contents, without loss of any float gold. All the debris, even the iron sulphurets of the ore, is specifically lighter than the zinc ; and the ore, introduced at the bottom of a deep and narrow trough of melted zinc, rises to the surface to he removed, leaving in its passage the gold behind as an alloy,which can be tested at any time, and the amount of gold in it determined with accuracy. When sufficiently rich, the precious metals are separated from the zinc by retorting, or the known modes of dissolving the zinc by acids. No water is required in the zinc process above explained, except for the use of the engine, to reduce the ores, and that much is found even in the barren Colorado desert without difficulty. This point is well worthy of consideration, for niiiH out of ten rich gold mines are now lying idle,entirely or part of the time, for want of water required for the usual battery amalgamation works, while the sagebrush and mesquite of the desert yields ample fuel to raise steam and to keep the zinc up to the required temperature—just above the melting point; and the value of the float gold saved is alone sufficient to cover the whole cost of extraction bv zinc.