Pyrite, marcasite, sphalerite and galena. Navan, Ireland
Sphalerite (dark grey, bottom left) is overgrown by banded pyrite (yellow-white, centre) and marcasite (blue-white), which shows reflection pleochroism (blue-white to white-blue, centre top) and bireflectance. The outer growth zone of marcasite is overgrown by a thin band of low reflectance pyrite (brown, centre). Minor amounts of galena (blue-grey, lower reflectance than pyrite, centre bottom) occur within sphalerite.
Polished block, plane polarized light, x 160, oil