Pyrrhotite, pyrite, arsenopyrite, native gold and TiO2 mineral. Witwatersrand, Republic of South Africa

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Pyrite (light yellow, right centre) and fractured arsenopyrite (light blue-white, top centre) are cemented by pyrrhotite (brown, bottom centre). A gold grain (golden-yellow, very high reflectance, centre top) is close to a single crystal of a TiO2 mineral (grey, centre top). Other small crystals of pyrite, arsenopyrite and TiO2 occur within pyrrhotite. Quartz (left) has internal reflections. The colour and reflectance of gold in this photomicrograph closely approach its appearance under the microscope.

Polished block, plane polarized light, x 160, oil

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