Sphalerite, chalcopyrite, pyrite, galena and marcasite. Nenthead, North Pennines, Britain

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Sphalerite (light grey, bottom left) and chalcopyrite (yellow, top right) are the major sulphides. Pyrite (light yellow, centre) is euhedral to subhedral and is intergrown with minor marcasite (white, centre right), which is difficult to see, and with chalcopyrite, sphalerite and galena (blue-white, centre left). Chalcopyrite (centre) contains a small lath-shaped inclusion of galena. Differences in reflectance in the galena are due to different amounts of tarnish (centre, centre left). Quartz (dark grey) is euhedral (top left) and shows faint internal reflections (top centre). Black areas are polishing pits.

Polished block, plane polarized light, x 80, air

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