Bornite and chalcocite. Gortdrum, Ireland
Bornite (pink-brown) is complexly intergrown with white copper sulphide, chalcocite (centre). Anhedral quartz (dark grey, top right) and euhedral dolomite (light grey, centre) are the main gangue phases. Dolomite rhombs show bireflectance from lighter grey (centre) to darker grey (top centre), but have higher reflectance than quartz. Black areas are polishing pits.
Polished block, plane polarized light, x 80, air