Show GOLD FROM BLACK SAND TAILINGS by john gross the alaska station of the bureau of mines has recently conducted tests on two tailings from black sand which had been treated previously at the station the results of this previous treatment have been given in a paper entitled recovery of gold from black sand by classifier classifier concentration the gold in these tailings was intimately united with quartz and was so finely divided that it could not be detected with the naked eye nor even by panning unless the material was ground its fineness is further shown by the assay result which reported only 12 per cent of the gold content as whereas the assay of the original sand reported 36 per cent of the gold as the fact that the gold was in such fine particles closely united with quartz precluded further recovery by amalgamation without grinding on the other hand the small content present as well as the lack of grinding appliances at the placer mines of alaska made it necessary that the material be cheaply handled if at all with these facts in mind the experiments described below were undertaken coarse tailing this tailing had been obtained by amalgamating ga mating the concentrate produced by classifier concentration the tailing was screened on a 28 mesh screen the oversize was hand jigged on a 6 inch by 6 in screen resulting in a concentrate and a tailing the undersize was passed over a canvas table resulting in a concentrate and a tailing the results of this experiment were as follows weight per cent assay gold contents contents pounds weight oz per ton gold oz gold tao jig concentrate 62 56 2625 O jig tailing canvas concentrate 47 43 11 13 23 canvas tailing 90 1100 1000 32 1000 from these results evidently a fair degree of concentration may be obtained on the coarser portion but not in the finer A test showed that the gold in the jig concentrate can be recovered by amalgamation if the concentrate is previously ground but without grinding the recovery is negligible fine tailing this tailing had been obtained from the concentration of minus 30 mesh material on a canvas table the tailing was again passed over a canvas table the aim being to produce a small amount of concentrate the results obtained are as follows by a second treatment on a canvas table A test showed that an excellent recovery can be obtained on this concentrate by amalgamation in a revolving barrel but whether barrel amalgamation would pay on such low grade material is doubtful conclusions these experiments demonstrate that on material of this nature an enriched product may be obtained by hand jigging the coarser sand and by canvas table concentration of the finer sand the enriched product of the coarser sand is worthless unless ground and amalgamated if produced in sufficient quantity however it could be profitably shipped to a smelter in the placer mines of alaska the amount of black sand produced by each operator generally is small treatment for recovery of any gold not ordinarily obtained by classifier and canvas table concentration followed by barrel amalgamation or the resulting concentrates would be profitable only when handling large amounts of black sand the gold in the enriched product of the finer sand can be recovered by barrel amalgamation ga mation 0 weight pounds per percent ent assay gold ifan contents ten t s con content tep canvas concentrate weight 54 oz per ton gold oz gold clo canvas tailing 1986 2100 1000 1000 these results show that an additional reco recovery can be obtained on this material metallurgist U S bureau of mines |