Pentlandite, pyrite, chrome-rich spinel, magnetite and chalcopyrite. Kambalda, Western Australia
Pentlandite crystals (light brown, centre left) with cleavage along (111) are replaced by pyrite (light yellow, higher reflectance) and chalcopyrite (tarnished to dull yellow, centre). Zoned euhedral spinel crystals (bottom) comprise chrome-rich cores (ferrochromite) (light grey-green) and magnetite rims (brown-grey). A small chalcopyrite crystal (yellow, bottom) is untarnished and shows its true surface colour and reflectance. Silicates are dark grey.
Polished block, plane polarized light, x 90, air