TiO2 minerals, chalcocite and chalcopyrite. Wales, Britain
A metadolerite where an original titanomagnetite with oxidation-exsolution ilmenite lamellae has been altered to TiO2 minerals (light grey, right), which have replaced the ilmenite, accompanied by the complete removal of the magnetite component (faint orange-stained areas). Later chalcopyrite (yellow, centre right) and chalcocite (blue, centre left) have overgrown TiO2. The TiO2 minerals show faint reflection pleochroism (left) between adjacent crystals.
Polished block, plane polarized light, x 160, oil