Pyrite, chalcopyrite, galena, marcasite and native gold. Çeyeli, Turkey

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Marcasite (light blue-white, bottom right) rhombs form the cores to pyrite crystals (light yellow-white, right), which are replaced by chalcopyrite (top right). One marcasite crystal (bottom right) is twinned and shows faint bireflectance and reflection pleochroism (grey to blue-grey). Pyrite is rimmed and replaced by chalcopyrite (yellow), which itself has a galena rim (blue-grey, centre). Native gold (light yellow, high reflectance, centre) is intergrown with galena. The low reflectance and blue-grey colour of galena against native gold is characteristic. The black area is resin-

Polished block, plane polarized light, x 160, oil

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