Pyrite, sphalerite and galena. Ireland

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This section is tarnished. Sphalerite (light grey, left and right) and galena (white, bottom left) are only slightly tarnished or untarnished. Pyrite is extensively tarnished and shows delicate growth zones as banding. On repolishing only the outermost growth bands are seen. The tarnishing shows the direction of growth and that pyrite has been fractured and re-cemented and/or replaced by galena and sphalerite. These textures would be more difficult to demonstrate after repolishing.

Polished block, plane polarized light, x 45, air

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