Pyrite, marcasite, violarite and pentlandite. Bushveld, Republic of South Africa
A crystal of pyrrhotite formerly carried pentlandite flames and a rim of granular pentlandite but both minerals are now completely altered. Trace amounts of relict pentlandite (brown, centre left) remain but most has been altered to violarite (brown and poorly polished, centre left). Small areas of violarite (disc-shaped, poorly polished, centre top) within pyrite/marcasite mark the former presence of pentlandite flames. Pyrrhotite has altered along (0001) planes to zwischen-produkt (lower reflectance, centre bottom), and to pyrite and marcasite (yellow-white, centre top). Dark grey areas are silicates.
Polished block, plane polarized light, x 80, air