Arsenopyrite, wolframite and covelline. Cligga Head, Cornwall, Britain

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Euhedral arsenopyrite (white, high reflectance, centre) is extensively altered to covelline (blue, bottom left). Wolframite (brown-grey, top right) is poorly polished with many polishing pits (black) and shows faint zoning with blue-grey cores and brown-grey margins (right centre); this is difficult to see. Dark grey areas are quartz.

Polished block, plane polarized light, x 80, air

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