Sphalerite, tetrahedrite group mineral, chalcopyrite and galena. Çeyeli, Turkey
Sphalerite (grey) shows a slight variation in reflectance and very faint reddish internal reflections (both very difficult to see) due to submicroscopic inclusions of tetrahedrite (right centre). Coarse-grained tetrahedrite (green-blue, centre left) is also present within sphalerite as is chalcopyrite (yellow, bottom left). A minor amount of galena (white) lies in the gangue between sphalerite crystals (bottom right).
Polished block, plane polarized light, x 160, oil