Cinnabar (and pyrite). Mount Amiata, Italy
This is the same field of view as 41e but with partially crossed polars. Pyrite is no longer visible. Cinnabar crystals show strong anisotropy (bottom left), but the anisotropy colours are largely masked by strong red internal reflections (centre bottom). The grain size difference between single crystals and aggregates of cinnabar is clearly seen.
Polished block, partially crossed polars, x 80, air