Uraninite, pyrite, chalcopyrite and safflorite. Tyndrum, Scotland
Uraninite (light, grey-brown, top) shows collomorphic banding along its margins (top left), seen by slight variations in reflectance. Pyrite (light yellow-white) is poorly crystalline (top right, bottom right), whereas marcasite (white, bottom centre) is well polished and has a poorly developed lath-shaped habit. Anhedral chalcopyrite (yellow, top right) is common. The discrete crystal rim (white, centre left) has the habit of a replaced safflorite. Gangue silicates are dark grey, black areas are polishing pits.
Polished thin section, plane polarized light, x 80, air