Marcasite is one of the sulphides of iron. It often shows a white colour on a fresh surface. It is found in iron metallic veins and frequently with lead and zinc ores, and is also found in sedimentary rocks. Marcasite most frequently occurs as a replacement deposit in limestone and often in concretions imbedded in clays, marls, and shales. It has a relative hardness of 7.
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