Cassiterite, arsenopyrite, tennantite, sphalerite, chalcopyrite and covelline. Mount Pleasant, New Brunswick, Canada

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Euhedral rhombic arsenopyrite (white, high reflectance, top centre) is partially intergrown with euhedral equant crystals of cassiterite (grey, bottom centre) which show faint bireflectance (bottom centre). Sphalerite (medium brown-grey, centre) has very fine chalcopyrite inclusions and shows lower reflectance than tennantite (blue-grey, right), which has a small chalcopyrite (yellow) crystal on its margin. A small crystal of chalcopyrite (top left) has altered to covelline (deep blue, top left). The main gangue is silicate (dark grey) with polishing pits (black). An accessory mineral, zircon, with higher reflectance than the silicates (left centre), lies close to one of the pits.

Polished block, plane polarized light, x 80, air

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