Pyrite, marcasite, chalcopyrite and sphalerite. Galapagos Mound, Pacific Ocean

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Pyrite (light yellow-white) forms euhedral crystals (centre) which contain small sphalerite (light grey, centre right) inclusions or is interbanded with marcasite (blue-white, higher reflectance than pyrite, centre top, top right). The lower reflectance growth bands within the pyrite-marcasite intergrowths are either due to very fine-grained pyrite or the presence of small non-sulphide inclusions. Anhedral chalcopyrite (yellow, centre) is present within the silica matrix. Black areas are polishing pits.

Polished block, plane polarized light, x 80, air

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