Galena, sphalerite and covelline. Alderley Edge, Cheshire, Britain
Galena (white, centre) has characteristic triangular pits due to plucking along the (100) cleavage. Sphalerite (light grey, centre top) is euhedral to subhedral and intergrown with galena. Minor amounts of covelline (deep blue, centre right) are associated with the alteration of galena and show its original grain size. Quartz crystals (dark grey, left, top) have euhedral terminations. Smaller euhedral quartz crystals (centre right) within galena show strong internal reflections. A rock clast (dark grey, bottom right) occurs within pitted coarse grained baryte (medium grey, bottom). Black areas arc polishing pits.
Polished block, plane polarized light, x 80, air