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

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Pyrite aggregates (pale yellow-white, top) have been fractured. These fractures have been infilled by chalcopyrite (yellow, bottom right), galena (blue-white, centre left) and covelline (blue, top left). Sphalerite (light grey, left) carries unoriented chalcopyrite and euhedral pyrite inclusions (left). The central aggregates of covelline have relict chalcopyrite (centre bottom left) within them and show intense bireflectance and reflection pleochroism (light to dark blue). Quartz is dark grey (top right), black areas are polishing pits.

Polished block, plane polarized light, x 80, air

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