Hematite is a common iron oxide compound with the formula, Fe2O3 and is widely found in rocks and soils. Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of Fe2O3. It has the same crystal structure as corundum (Al2O3) and ilmenite (FeTiO3). With this it forms a complete solid solution at temperatures above 950 °C (1,740 °F). Hematite naturally occurs in black to steel or silver-gray, brown to reddish-brown, or red colors. It is mined as an important ore of iron. It is electrically conductive.