Siderite

A widespread mineral, SIDERITE is an important industrial source of iron. It is formed just below the earth's surface and has no extraterrestrial sources. SIDERITE's chemical composition makes it an ideal source of iron. In practice, however, its use is restricted, as it rarely occurs in sufficient quantities to make commercial extraction profitable. Externally it may have a strong resemblance to calcite, but the two species can be distinguished by acid testing. Because of its iron content, SIDERITE becomes magnetic when heated. SIDERITA is widespread but rarely common, which means there are many small deposits but few industrially useful.