Digenite, bornite, wittichenite, haematite, covelline and chalcopyrite. English Lake District, Britain

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Digenite (blue) is replaced along cleavage and fractures by covelline (deep blue, centre left) and about its margin by bornite (brown-pink, centre) and wittichenite (cream-white, centre right). Much of the wittichenite is associated with fine-grained haematite (green-grey, centre top), with fractures cutting digenite having a central haematite core and wittichenite margins (centre left). A small intergrowth of chalcopyrite (yellow) and bornite (brown) is crystallographically controlled (top centre). Quartz is dark grey, black areas are polishing pits.

Polished block, plane polarized light, x 40, air

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