Chalcopyrite, sphalerite and covelline. Alderley Edge, Cheshire, Britain

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Chalcopyrite (yellow, centre top) is the main cement and is altered along its edges to covelline (deep blue, centre left) and limonite (medium grey, centre top). Sphalerite (light grey, centre top, centre left) occurs as small inclusions within chalcopyrite. Quartz (dark grey) and feldspar (dark grey with cleavage, bottom left, bottom right) show faint light-coloured internal reflections. Black areas are polishing pits.

Polished block, plane polarized light, x 80, air

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