Pyrite, arsenopyrite, sphalerite, chalcopyrite and galena. English Lake District, Britain

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Euhedral rhombic arsenopyrite (white, high reflectance, centre), showing faint reflection pleochroism (centre right), is enclosed within a fine-grained mosaic of pyrite (light yellow). Sphalerite (light grey, bottom left) has abundant chalcopyrite (yellow) inclusions in its cores but has inclusion-free rims (bottom left). Quartz gangue (top right) is dark grey.

Polished block, plane polarized light, x 40, air

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