Pyrite, native gold, sphalerite and carbonaceous matter. Dolgellau Gold Belt, Wales, Britain
Pyrite (light pink-blue, centre) contains abundant native gold (yellow, centre) inclusions and minor sphalerite (light grey, centre bottom) on its margin. A larger inclusion-free sphalerite (left) is present. A curved lath of carbonaceous matter (medium grey, lower reflectance than sphalerite, centre right) rims a void (black). Quartz, the main gangue, shows faint internal reflections (top left). Black areas are voids and polishing pits. The gold is 800 fine. Specimen number BM077R44. British Museum Collection.
Polished block, plane polarized light, x 80, air