Uraninite and chalcopyrite. Tyndrum, Scotland

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Collomorphic banding in uraninite is seen as variations in surface colour and reflectance (centre top). Later, uraninite, overgrowing the main banded uraninite, is being replaced by secondary uranium-bearing phases (grey, reflectance similar to the gangue, centre top). Trace amounts of chalcopyrite (yellow, top left) are present. The gangue shows strong light-coloured internal reflections.

Polished thin section, plane polarized light, x 160, oil

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