Pyrite, marcasite, galena and sphalerite. Shullsburg, Wisconsin, USA

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A euhedral pyrite (yellow-white, right) crystal has a pyrite overgrowth forming a rim (bottom right) that has a slightly higher reflectance. Pyrite is replaced along its cleavage by galena (blue-white, centre) and minor sphalerite (dark grey, Centre). A tabular crystal of marcasite (white-yellow, centre bottom) has higher reflectance than pyrite, and also is extensively replaced by galena and sphalerite which exactly pseudomorph the original marcasite crystal. Black area is carbonate gangue.

Polished block, plane polarized light, x 160, oil

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