Pyrite, chalcopyrite and covelline. El Salvador, Chile
Subhedral to anhedral pyrite (pale yellow-white, left) carries silicate inclusions (left centre) and is surrounded by chalcopyrite (yellow, centre), which is extensively altered to fine-grained covelline (blues, centre right). Covelline shows bireflectance and reflection pleochroism from dark to light blue (centre). Quartz is the main silicate (top centre).
Polished block, plane polarized light, x 40, air