Columbite, pyrite and zircon. Greisenized granite. Ririwai, Nigeria
Two columbite crystals (brown, centre left and right) have small zircon crystals (medium grey) growing around them. A discrete zircon (centre top) with a thin pyrite rim lies between the columbites. Fine-grained secondary pyrite (yellow, high reflectance, centre) infills voids in fluorite (dark grey with polishing pits, centre). Chlorite (green-grey, bottom centre) and quartz (medium grey, right) are the main silicates. Finely disseminated haematite is responsible for the 'high' reflectance of chlorite. Black areas are polishing pits.
Polished block, plane polarized light, x 160, air