Pentlandite, chromite, nickel arsenide, ferrichromit and heazlewoodite. Unst, Shetland Islands, Britain
Chromite (dark grey, left) has thin spongy ferritchromit rims (lighter grey, top centre). Pentlandite (brown-yellow, centre bottom) shows its characteristic cleavage and surrounds a grain of pink nickel arsenide (centre right). Pentlandite is altering along fractures to heazlewoodite (white, higher reflectance, centre top) Silicates are black.
Polished block, plane polarized light, x 160, air