Pyrite, marcasite, sphalerite and galena. Navan, Ireland

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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

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