Zircon, rutile and columbite. Greisenized granite. Ririwai, Nigeria
125µm
A typical association of ore and accessory minerals in altered mica. Zircon crystals (dark grey, centre left, right centre) are euhedral to subhedral and show faint internal reflections and zoning with lower reflectance outer zones. Rutile grains (light grey, highest reflectance) enclose lower reflectance cores of rounded columbite (brown-grey, centre top). An aggregate (centre top left) comprises two rounded zircon crystals (grey, low reflectance) surrounded by rutile on their left and columbite on their right. The main matrix is altered brown mica. Black areas are polishing pits.
Polished block, plane polarized light, x 160, air
