Magnetite, molybdenite and pyrite. Henderson Mine, Colorado, USA
Subhedral magnetite crystals (brown-grey, centre right) enclose small rounded pyrite crystals (white, high reflectance) and a cube of pyrite (centre left). Curved laths of molybdenite show strong bireflectance from dark grey (when oriented north-south, bottom left) to light grey (oriented east-west, top left). Quartz shows strong internal reflections.
Polished block, plane polarized light, x 160, oil