Columbite, rutile, zircon and xenotime. Greisenized granite. Ririwai, Nigeria
250µm
Columbite (brown-grey, centre) is enclosed within a higher reflectance rutile (light grey, with fractures). A subhedral zircon (dark grey, centre bottom) is intergrown with both phases. Discrete, euhedral to subhedral rutile and zircon which shows internal reflections (top right) have grown within lath-shaped chloritized mica (blue-grey, top right). A euhedral zircon (right centre) has a rhombic euhedral xenotime growing from it into chlorite, but the slight differences in reflectance (xenotime is lower) are difficult to see at this magnification. Quartz and chlorite (grey-green, bottom left) are the main silicates. Black areas are polishing pits.
Polished block, plane polarized light, x 160, air
