Telluride, tetradymite group
Specific gravity: 8.91
Common impurities: Se,S
Hedleyite is typically a late-stage hydrothermal mineral in quartz veins and massive
sulphides associated with skarn and breccia; less
commonly it occurs in pegmatites. Associated minerals include
sphalerite and pyrite
At Maldon, Mount Alexander Shire, Victoria, Australia, hedleyite has been found in the goldfield in blebs together with native bismuth (AJM 15.35).
São Sebastião das Águas Claras, Nova Lima, Iron Quadrangle, Minas Gerais, Brazil, is a recently discovered gold deposit in a greenstone belt. Part of its hydrothermal system is characterised by chaotically distributed tourmaline. Pyrrhotite and late chalcopyrite occur in the tourmaline-rich pockets. Bismuth, bismuth–gold intermetallic aggregates, and bismuth telluride minerals locally fill microfractures. Hedleyite and the unnamed mineral Bi8Te3 make up composite aggregates with joséite-B. The gold-bismuth-tellurium mineral assemblages indicate precipitation below about 270°C (CM 53.1061-1072).
At the type locality, the Goodhope mine, Hedley, Osoyoos Mining Division, British Columbia, Canada, the country rock is a skarn composed mainly of garnet, epidote and pyroxene, cut by irregular veins and stringers of quartz. Most of the hedleyite samples were in these quartz bodies, but some also were noted in the skarn. Associated minerals include sphalerite, quartz, bismuth, joséite, pyrrhotite, molybdenite, arsenopyrite, calcite, garnet, epidote, diopside and gold (AM 30.644, Mindat).
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