Bornite, magnetite, chalcopyrite, valleriite, TiO2 mineral and ulvöspinel. Palabora, Republic of South Africa

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Magnetite (light grey, top) carries small exsolved, euhedral inclusions of ulvöspinel (dark grey, top left). Bornite (pink brown, high reflectance, bottom) is replaced by chalcopyrite (yellow, bottom left) which forms laths and irregular lamellae. Valleriite (brown and medium grey, low reflectance, centre bottom) forms incomplete rims around the copper-iron sulphides. Small lath-shaped crystals of a TiO2, mineral (light grey, reflectance similar to magnetite, left centre) occur within the gangue. The gangue comprises silicate (hard, faint internal reflections, centre), a phyllosilicate (lowest reflectance, poor polish, centre) and carbonate. Black areas are polishing pits. Two adjacent crystals of valleriite show its extreme reflection pleochroism from yellow-brown (oriented east-west, centre bottom) to charcoal-grey (oriented north-south, centre right).

Polished block, plane polarized light, x 160, air

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