Chalcopyrite, pyrrhotite, cubanite and pentlandite. Stillwater. Montana, USA

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Pyrrhotite (dark brown, top right) has a well developed cleavage which extends into chalcopyrite (yellow, top centre and left) and cubanite (blue-grey, centre right) areas, suggesting that chalcopyrite and cubanite are replacing pyrrhotite. Dark brown areas within chalcopyrite are relict pyrrhotite (bottom left). Pentlandite (pale brown-white, bottom) forms flames which are parallel with the basal (0001) cleavage of pyrrhotite. Silicates are black.

Polished block, plane polarized light, x 160, oil

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