Pyrite and zircon. Vaal Reef, Witwatersrand, Republic of South Africa
Rounded pyrite (yellow-white) grains comprise single crystals, grains with poorly crystalline pyrite cores (top centre), framboidal grains (centre bottom right) and recrystallized framboids (centre top right). Many pyrite grains are fractured. Two rounded zoned zircons (light grey, centre) are present. Galena, arsenopyrite, rutile and altered uraninite are also present but cannot be distinguished at this magnification.
Polished block, plane polarized light, x 80, air