Iron ores are rocks and minerals from which metallic iron can be economically extracted. The ores are usually rich in iron oxides and vary in color from dark grey, bright yellow, deep purple, to rusty red. The iron itself is usually found in the form of magnetite (Fe
4), hematite (Fe
3), goethite (FeO(OH)), limonite (FeO(OH).n(H2O)) or siderite (FeCO3).