Bravoite, nickeliferous pyrite, marcasite, smithsonite and limonite. Oxclose Mine, South Pennines, Britain

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Bravoite (pink-brown) is euhedral (top right) to anhedral (centre bottom) and has lower reflectance than nickeliferous pyrite (light brown-white, centre bottom) which overgrows it. Both phases are earlier than marcasite (light green-white, bottom right). Smithsonite (light greys, bottom centre) shows bireflectance between adjacent crystals. Bravoite has altered to limonite (light grey) along growth zones (centre top) and twin planes (top right, in euhedral bravoite). Dark grey areas are fluorite (centre) crystals. Black areas are polishing pits.

Polished block, plane polarized light, x 80, air

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