Magmatic sulphide ores
Pentlandite, pyrrhotite, pyrite and chalcopyrite. Bushveld, Republic of South Africa
Pentlandite (brown-yellow, top) shows its typical (111) cleavage and is intergrown with pyrrhotite (pink-brown, centre, centre right). Fine-grained pyrite (light yellow, top right) intergrown with chalcopyrite (yellow, top right) forms incomplete rims between pentlandite and pyrrhotite. Dark grey areas are silicates with fine sulphide veinlets lying along their cleavages, black areas are polishing pits.
Polished block, plane polarized light. x40, air
Pentlandite, pyrrhotite, pyrite and chalcopyrite. Bushveld, Republic of South Africa
Pentlandite (brown, top centre) with (111) cleavage is intergrown with pyrrhotite (pink-brown, top right). Chalcopyrite (yellow, centre right) and pyrite (pale yellow-white, centre) form rims around pentlandite. Black areas are polishing pits, the dark grey area is the mounting resin with small round gas bubbles (black, bottom left).
Polished block, plane polarized light. x40, air
Pentlandite, chalcopyrite, pyrite and pyrrhotite. Merensky Reef. Bushveld, Republic of South Africa
Pentlandite (light brown, centre) is intergrown with chalcopyrite (yellow, right), pyrite (pale yellow-white, centre bottom) and minor amounts of pyrrhotite (lilac-grey, centre right). Silicate gangue (grey) shows internal reflections. Black areas are polishing pits. The sulphides are interstitial to the silicates.
Polished block, plane polarized light, x 80, air
Pyrrhotite, pentlandite and chalcopyrite. Bushveld, Republic of South Africa
Pyrrhotite (brown, centre) has coarse-grained pentlandite crystals (light brown, high reflectance) about its margin (left centre) and fine-grained pentlandite as a flame-like exsolution body (centre right) below chalcopyrite (yellow, centre right). Smaller pentlandite flames are seen along the top and bottom margins of the pyrrhotite. Silicates are dark grey.
Polished block, plane polarized light, x 80, air
Pyrrhotite (brown-pink, right) enclosing chalcopyrite (yellow) has a larger pentlandite (brown, higher reflectance) crystal on its right hand margin. An original chalcopyrite, pyrrhotite and pentlandite intergrowth (left) now comprises unaltered chalcopyrite (yellow, left centre), very fine-grained alteration products after pyrrhotite the so called zwischen-produkt (white with cleavage, centre left) and violarite (dark brown and poorly polished, centre bottom) after pentlandite. Grey areas are silicate phases, black areas are polishing pits.
Polished block, plane polarized light, x80, air
Cubanite, chalcopyrite, pyrrhotite, magnetite and pyrite. Bushveld, Republic of South Africa
Chalcopyrite (yellow, centre left) is intergrown with cubanite (light brown, centre) which forms broad and very fine lamellae within chalcopyrite as an exsolution texture. Pyrrhotite (brown, left centre) occurs on the margin of chalcopyrite, has a deeper surface colour than cubanite and shows reflection pleochroism. Magnetite (grey, left centre) shows cleavage. Minor amounts of pyrite (white, right centre) associated with magnetite lie within the chalcopyrite-cubanite intergrowth. Silicates are black. Cubanite and chalcopyrite can be difficult to distinguish from each other in plane polarized light.
Polished block, plane polarized light. x 160, oil