Sulphosalt, bismuth- and antimony- bearing mineral; antimony appears to be an essential component for the stabilisation of nuffieldite
Specific gravity: 7.01
Hardness: 3½ to 4
Streak: Greyish black
Colour: Grey, steel grey, greyish green, reddish brown
At the type locality, the British Columbia Molybdenum Ltd. mine, Patsy Creek, Kitsault, Alice Arm, Skeena Mining Division, British Columbia, Canada, the stock is composite, and consists of granodiorite, quartz diorite, alaskite, granodiorite porphyry and related breccia. The intrusion is intimately veined by a quartz stockwork in which molybdenite is the most important economic mineral. The metallic minerals common to most of the quartz veins include molybdenite, pyrite, galena, sphalerite, chalcopyrite, pyrrhotite, tetrahedrite, cosalite and aikinite. The quartz vein containing the nuffieldite differs from the others in that it lacks chalcopyrite, pyrrhotite and tetrahedrite. The vein is 1 inch wide and contains small pyrite cubes and molybdenite flakes along the edges; the sulphosalt crystals are in 1-3 mm diameter vugs. Only two of the vugs were found to contain nuffieldite. The other vugs contained cosalite, aikinite and a new sulphosalt mineral. The only metallic mineral observed in contact with nuffieldite is aikinite (CM 9.439-452).
At the Maleevskoe deposit, Altai Krai, Russia, nuffieldite is reported from a pyrite-rich massive sulphide deposit, as microscopic platy crystals and as aggregrates of grains up to 0.6 mm within a copper-zinc rich zone. Associated minerals include hessite, tetradymite, electrum, aikinite, lindströmite, hammarite, cosalite, kobellite, galenobismutite, gudmundite, berthierite and nisbite (CM 32.359-364).
At the Alaska Mine, Poughkeepsie Gulch, San Juan county, Colorado, USA, nuffieldite is associated with neyite, galena, tetrahedrite, chalcopyrite and sphalerite (HOM).
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