Pyrite, chalcopyrite, sphalerite, covelline and galena. Parys Mountain, Britain

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Euhedral pyrite crystals (pale yellow-white, bottom centre) have relict poorly polished cores (top left), suggesting that they have recrystallized. Chalcopyrite (yellow, centre), which has altered to covelline (blue, centre right and left) about its crystal boundaries, is intergrown with sphalerite (light grey, left). Sphalerite contains abundant chalcopyrite inclusions aligned along crystallographic directions (left) and has suffered chalcopyrite disease. A single grain of galena (white, centre left) is intergrown with sphalerite. Dark grey areas are quartz, black areas are polishing pits.

Polished block, plane polarized light, x 80, air

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