Pyrrhotite, pentlandite and chalcopyrite. Stillwater, Montana, USA

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Pyrrhotite (brown) has pentlandite (light brown, higher reflectance, centre) exsolution bodies as flames, aligned along (0001). Minor amounts of chalcopyrite (yellow, centre right) are associated with cleavage and fractures within pyrrhotite. Silicates are black.

Polished block, plane polarized light, x 160, oil

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