Magnetite is a ferrimagnetic mineral with chemical formula Fe₃O₄, one of several iron oxides and a member of the spinel group. The chemical IUPAC name is iron(II,III) oxide and the common chemical name is ferrous-ferric oxide. The formula for magnetite may also be written as FeO·Fe₂O₃, which is one part wüstite (FeO) and one part hematite (Fe₂O₃). This refers to the different oxidation states of the iron in one structure, not a solid solution. The Curie temperature of magnetite is 858 K (585 °C; 1,085 °F). It is black or brownish-black with a metallic luster, has a Mohs hardness of 5–6 and a black streak.