Chalcocite, bornite and TiO2 mineral. Gortdrum, Ireland
Bornite (brown-pink) and white copper sulphide, chalcocite, show a coarse symplectite-like intergrowth. Veinlets of a TiO2 mineral (light grey, bottom), associated with fine-grained bornite and chalcocite, cross-cut the gangue. This comprises rhombic dolomite, showing bireflectance from lighter to dark grey (centre, centre left). Black areas are polishing pits.
Polished block, plane polarized light, x 80, air