Pyrite, chalcopyrite, pyrrhotite, native gold. Vaal Reef, Witwatersrand, Republic of South Africa
Pyrite (light yellow) encloses small inclusions of chalcopyrite (yellow, centre right), pyrrhotite (brown, centre left) and a mixed chalcopyrite-pyrrhotite (centre top) inclusion. A small native gold grain (golden yellow, high reflectance, centre right) is also present and has a higher reflectance than chalcopyrite. Quartz is dark grey.
Polished block, plane polarized light, x 160, oil