| Abstract | (Summary)
The ore sample contained tungsten, molybdenum and bismuth in economical amount with the following head assays: 1.02% W0?, 0.44% MoS? and 0.17% Bi. The tungsten occurred mainly as
wolframite, the molybdenum as molybdenite, and the bismuth as native metal and bismuthinite. The wolframite and molybdenite had coarse mineralization (50 microns to 15 millimeters), whereas the bismuth minerals, at less than 50 microns in size, were
finer-grained. Pyrite, marcasite and pyrrhotite were the main metallic impurities in the ore. Grinding to minus 48 mesh was sufficient for liberation. At this fineness, 89% of the tungsten, 94% of the molybdenite and 85% of the bismuth were recovered
in rougher concentrates. The wolframite was concentrated by gravity (either jigging, spiralling or tabling), while the molybdenite and bismuth minerals were recovered by selective flotation. Because of the friable nature of the bismuthinite and the
native bismuth, it was not necessary to regrind the ore prior to their concentration. To meet market specifications, it was necessary to upgrade the rougher concentrates by the following techniques: (1) tabling, magnetic separation and roasting (for
desulphurization) of the tungsten concentrate; (2) cleaner flotation and acid leaching for the molybdenite concentrate; (3) gravity concentration or flotation-separation for the bismuth. |