Bornite, chalcopyrite, magnetite and TiO2, mineral. Palabora, Republic of South Africa
Bornite (brown) is intergrown and replaced by chalcopyrite (yellow) along (100), some of which forms irregular spindle-shaped lamellae growing from the margin of bornite towards its centre. Magnetite (light grey, right) is inclusion-free. Small TiO2. crystals (medium grey, top centre) have lower reflectance than magnetite. Silicate minerals (centre left, top left) have lower reflectance than trigonal carbonate (centre), which shows bireflectance associated with polysynthetic twinning. Pseudobrookite, rather than rutile, is the main TiO2, mineral at Palabora.
Polished block, plane polarized light, x 80, air