Sphalerite, chalcopyrite, pyrrhotite and galena. Great Gossan Lead, Virginia, USA
Sphalerite (light grey, right) has chalcopyrite inclusions aligned along crystallographic directions and about grain boundaries. Hence, it shows chalcopyrite disease. It is rimmed by chalcopyrite (yellow, centre) and pyrrhotite (brown, top left), together with minor galena (white, centre bottom). Dark grey area is silicate, black areas are polishing pits.
Polished block, plane polarized light, x 40, air