Siderite: Siderite, also called chalybite, iron carbonate (FeCO 3), a widespread mineral that is an ore of iron.; The mineral commonly occurs in thin beds with shales, clay, or coal seams (as sedimentary deposits) and in hydrothermal metallic veins (as gangue, or waste rock).; Manganese (Mn), magnesium (Mg), and calcium generally …Web