Altered pentlandite, pyrite, pyrrhotite, chalcopyrite and spinel. Kambaida, Western Australia

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Central pyrrhotite (brown) and euhedral spinel (ferrochromite) (grey, centre left) are surrounded by extensively altered pentlandite (light brown, abundant fine polishing pits, top) crystals. The alteration of pentlandite to violarite lowers its reflectance and alters its surface colour from brown-yellow to red-brown. Pyrite (light yellow, high reflectance, left) is intergrown with chalcopyrite (yellow, bottom right) and surrounds altered pentlandite. Dark grey areas are silicates, black areas are polishing pits.

Polished block, plane polarized light, x 80, air

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