MOSSBAUER INVESTIGATION OF GOLD-BEARING PYRITE-RICH CONCENTRATES

A gold-bearing pyrite-rich concentrate of a refractory ore from the Go lden Bear mine, northwestern British Columbia, and a pyrite-rich conce ntrate from Newhawk's west zone, Brucejack Lake area, northern British Columbia, containing 38 and 316 ppm Au and 0.57% and 0.19% As, respec tively, have been investigated using Au-197 and Fe-57 Mossbauer spectr oscopy. In the Golden Bear sample, the gold is mainly chemically bound in the pyrite with minor amounts present as an Au-Ag alloy, whereas i n the Newhawk sample, the gold occurs mainly as an Au-Ag alloy with a composition close to Au0.5Ag0.5 and is only partly bound in the pyrite . Having mean isomer shifts of +3.2 and +4.0 mm/s with respect to a Pt metal source, the gold in pyrite exhibits shifts similar to those obs erved for gold in arsenopyrite. The nature of the lattice sites occupi ed by the gold in pyrite is discussed.