Hematite is one of the most common minerals. The color of most red and brown rock, such as sandstone, is caused by small amounts of Hematite. It is also be responsible for the red color of many minerals. It can form as a sedimentary precipitate, a product of weathering of other iron rich minerals in soils and oxidized zones of ore deposits, as a primary mineral in hydrothermal veins, and as a metamorphic mineral.