Wüstit

Wüstit, also known as iron(II) oxide, is a compound with the chemical formula FeO. It is one of the three main iron oxides, the others being hematite (Fe2O3) and magnetite (Fe3O4). Wüstit is the highest temperature iron oxide and is stable only above 575 degrees Celsius (1067 degrees Fahrenheit). Below this temperature, it disproportionates into iron metal and magnetite.

Wüstit is black in color and has a cubic crystal structure. It is a non-stoichiometric compound, meaning that its chemical formula does not perfectly represent the ratio of iron to oxygen atoms. In wüstit, there are often vacancies in the iron lattice, leading to a range of compositions from Fe0.84O to Fe0.95O. This non-stoichiometry contributes to its unique properties.

This iron oxide is found naturally in some iron-rich meteorites and as a minor component in some terrestrial rocks. It is also formed during the industrial smelting of iron ore, where it is a transient intermediate phase. Wüstit plays a role in high-temperature chemical processes and is of interest in materials science and geology. Its magnetic properties are also noteworthy, although it is antiferromagnetic rather than ferromagnetic like magnetite.