GOLD EXTRACTION.

Otago Witness, Issue 919, 10 July 1869, Page 11

GOLD EXTRACTION.

Mr B. D'Heureuae, iha communication to the San Francisco Mining and Scientific Press, remarks that only one-half or thereabout of the gold is extracted by quicksilver from the ore j the rest is either carried away as float, gold by the water required for the batteries, or remains in the' tailings. This fact, known to every intelligent operator, should alone be sufficient to point out the imperative necessity of devising other extracting agents for that great majority of ore containing more than 20 dols to 25 dola per ton, but not rich enough to leave a profit by direct chlorination. The case, therefore, stands thus — What is required is an extracting agent that does the work complete, cheaper than chloride, and requiring no water to reduce the ore, except such as is needed for the engine. Zinc, of all substances in existence, has the greatest affinity for gold. Its action, in a melted state, on gold is to instantaneously dissolve the same in any proportion. Its specific gravity, about 7, is sufficiently high to float all debris, not excepting sulphuret of iron, the constant companion of gold. It melts at a comparatively low temperature, and requires but little heat to retain its melted state. It is sufficiently volatile to permit of retorting, as in the use of quicksilver, but by a covered surface, and a temperature below a dark red heat, the loss by volatilisation and burning is hardly appreciable, while the metal is obtained at a low price, and in any quantity required. Thus we have in zinc a material manageable* and fulfilling the conditions required of a gold extracting agent in a high degree, higher than any other known. Mr D. Heureuse's mode of applying it consists simply 'in gradually introducing the gold-bearing pulverised substance below the aurfaca into a bath of melted zinc, which will immediately attack and dissolve nearly or every particle of gold, while the debris rises to the surface to be taken off. ..'-"The mechanism is very Qimple and durable. Should sulphurets, in which particles of gold are so firmly embedded aa not to offer any contact even on the smallest point, prevent the extraction to such a degree that it will pay to work it over by concentration, roasting, and chlorination, it may be done. But all the gold, in another manner lost as float gold, and much more, is certainly saved by the zinc. Dry crushers should be used in preference.