Cassiterite and molybdenite. Glen Gairn, Scotland
Coarse-grained cassiterite (light grey, left) is intergrown with radiating laths of molybdenite which show bireflectance and reflection pleochroism (brown-grey to grey, top right). The main silicates are coarse-grained white mica with cleavage (top left) and quartz (bottom right). Black areas are polishing pits.
Polished block, plane polarized light, x 40, air