Chloanthite, rammelsbergite, argentopyrite, pyrargyrite, safflorite, acanthite and pyrite. Tynebottom Mine, North Pennines, Britain

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Chloanthite (cream-white, pitted, right) has slightly lower reflectance than rammelsbergite (centre left), which shows faint reflection pleochroism from pink-white to cream-white. Rammelsbergite is overgrown by euhedral rhombs of safflorite (light blue-white, top centre left, centre left, next to pyrargyrite). Sector-twinned argentopyrite (centre) shows reflection pleochroism from light to dark brown and is intergrown with blue pyrargyrite (centre). Argentopyrite is extensively altered (left) to a mixture of pyrite, marcasite and an unnamed mineral of composition AgFe8S11 which cannot be distinguished from each other at this magnification; they are themselves intergrown with acanthite (blue-grey, lower reflectance than pyrargyrite, left centre).

Polished block, plane polarized light, x 180, oil

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