Chalcocite. arsenopyrite, chalcopyrite and bornite. Wheal Jane, Cornwall. Britain
The section is tarnished. Euhedral rhombic arsenopyrite (white) is fractured and replaced by chalcocite. Chalcopyrite (tarnished to yellow-red) is replaced by Bornite (tarnished to purple-brown) and chalcocite (pale blue) which is untarnished. Quartz and tourmaline (dark grey) are the gangue minerals. Black areas are polishing pits.
Polished block, plane polarized light, x 80, air