Pyrite, pyrrhotite, magnetite and chalcopyrite. Ducktown, Tennessee, USA
Pyrite (yellow-white, top) is surrounded by pyrrhotite (brown, top right), showing cleavage (black, top right), or forms small euhedral crystals within pyrrhotite (bottom left). Magnetite (light grey, top left) is euhedral and has pyrrhotite inclusions (bottom right). Amphibole (dark grey) has a partial rim of chalcopyrite (yellow, centre left) and inclusions of chalcopyrite, pyrrhotite and pyrite.
Polished block, plane polarized light, x 40, air