Chalcopyrite, pyrite, sphalerite and tetrahedrite group mineral. Neves-Corvo, Portugal
Pyrite (light yellow, high reflectance) forms euhedral crystals (bottom right) and fine-grained aggregates of relict pyrite (poorly polished, centre left) within chalcopyrite (yellow). Tetrahedrite (light blue-grey, centre) is enclosed within sphalerite (light grey, centre) rims.
Polished block, plane polarized light, x 80, air