Pyrrhotite, violarite and altered pyrrhotite. Kambalda, Australia
The primary ore was pyrrhotite and pentlandite but these minerals have suffered extensive supergene alteration. Relict pyrrhotite (brown, well polished, left, centre right) has an alteration rim of zwischen-produkt (light brown-white, highest reflectance, right bottom) and clearly shows that the alteration of pyrrhotite is crystallographically controlled along (0001). Pentlandite has been totally pseudomorphed by violarite (brown-white, finely pitted surface, centre) but its cleavage and crystal boundaries have been preserved. Silicates are black.
Polished block, plane polarized light, x 80, air