“SEM micrograph (SE mode) of a polished ore sample showing two concentrically zoned pyrite spherules (the slightly brighter core contains traces of Pb, Ag, Cu and As, probably all as nano-inclusions) in sphalerite (grey), with minor galena (white) and quartz (black).
Note the distinctly higher hardness of the pyrite.
Natural History Museum Vienna collection, catalogue no. E 6202 (dark, fine-grained, massive ore).
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Uwe Kolitsch - 25th March 2019