Cinnabar and pyrite. Mount Amiata, Italy
Aggregates of cinnabar (blue-grey) showing faint bireflectance and pink-blue to light blue reflection pleochroism (centre bottom) are more common than single subhedral crystals (centre top). Trace amounts of euhedral pyrite (light yellow, high reflectance, centre) occur within cinnabar and the carbonate gangue.
Polished block, plane polarized light, x 80, air