Bismuthinite, chalcopyrite, wolframite and native bismuth. Viloco, Bolivia
Euhedral to subhedral wolframite (grey-brown, low reflectance, centre right) is fractured and shows alteration about its margins. Chalcopyrite (yellow, left) is intergrown with bismuthinite (top centre), which shows strong reflection pleochroism (grey-blue to blue-white),and bireflectance. Poorly polished native bismuth (cream-white, high reflectance, centre) occurs within bismuthinite. Silicate phases are black.
Polished block, plane polarized light, x 160, oil