Chalcopyrite, tetrahedrite, pyrargyrite and pyrite. Sark's Hope Mine, Sark, Channel Islands, Britain
110µm
Altered euhedral tetrahedrite (light grey, left) is rimmed by chalcopyrite (yellow, centre). Chalcopyrite is zoned with inclusion-rich growth bands (lower reflectance) alternating with inclusion-free bands (centre). Pyrargyrite (blue, centre) has infilled a void between chalcopyrite crystals. Minor amounts of pyrite (pale yellow-white, high reflectance, bottom centre) have altered to limonite (grey) or form small framboids (bottom right, centre top) associated with tetrahedrite. Limonite (grey, top right) pseudomorphs after pyrite occur in chalcopyrite. Quartz is black.
Polished block, plane polarized light, x 180, oil
