| Description |
Before concentration tests were conducted on the Ontario ore for the recovery of the silver therein, specimens were studied microscopically to determine the physical characteristics of the ore and, if possible, the manner in which the silver existed. Measurements of the grains of the sulphide minerals were also made in order to determine the degree of crushing necessary to unlock the different minerals from each other. As the method of concentration will depend on the manner of association of the silver with the minerals in the ore, definite information concerning this relationship is absolutely necessary. The microscopic examination polished sections under reflected light afforded the best means for obtaining this information and was accordingly used. The silver in the ore was found as silver sulphides, presumably formed during the replacement of the silver-bearing tetrahedrite by galena. The silver minerals were closely associated with the galena and the tetrahedrite. The recovery of the silver is therefore dependent on the recovery of the lead and of the copper sulphides. No inclusions of silver minerals in either the pyrite or in the sphalerite could be found. The average size of the sulphide grains, as measured with a calibrated, net-ruled occular, was between 80 and 100 mesh (0.175 to 0.147 mm. in diameter(. Due to hte fact that the silver-bearing minerals cursh more readily than the non-silver-bearing minerals, grinding to minus 60 mesh (0.221 mm.) should be sufficient to unlock the minerals from each other and render then assemble to mechanical concentration. One possible obstacle to successful concentration of the ore is the alight alteration of galena to anglesite. This, however, was noticed in but a few sections and is probably of minor importance. The method of concentration, based on the result of this study, would involve the crushing of the ore to minus 60 mesh followed by flotation. This latter operation should recover the galena and the tetrahedrite, and therefore the silver. This material could be shipped to one of the lead smelters in the Salt Lake Valley and the full value of the silver in the concentrate could be obtained. |
