Zircon, thorite and xenotime. Albitite. Ririwai, Nigeria
The core of a large zircon crystal (light grey, highest reflectance, centre left) or aggregate of zircon crystals has been extensively replaced by mica (centre). The relict rim is both well crystalline (left) and vuggy (centre right). Thorite crystals (medium grey, reflectance higher than the silicates, faint internal reflections) have grown upon the relict zircon (top right corner of zircon and bottom right comer). A single rhombic-shaped euhedral crystal of xenotime (bottom right corner of zircon) has a similar reflectance to thorite and also shows internal reflections. Albite and mica (poorly polished, top left) are the main silicates. Black areas are polishing pits.
Polished block, plane polarized light, x 160, air