Digenite, bornite, haematite, covelline, wittichenite and chalcopyrite. English Lake District, Britain
250µm
Digenite (light blue, top) is replaced along cleavage by covelline (dark blue, centre left) and along grain boundaries by bornite (orange-brown, centre). A vein cross-cutting digenite is infilled with wittichenite (white, top left). Fine-grained haematite (green-grey) replaces copper and copper-iron sulphides (especially bottom right). Very fine-grained banded haematite (green-grey, low reflectance, centre) is associated with quartz (dark grey). Minor amounts of chalcopyrite (yellow, centre bottom) are surrounded by a haematite rim. Black areas are polishing pits. Quartz (dark grey) is the main gangue phase.
Polished block, plane polarized light, x 80, air
