Ferrous oxide, also known as iron(II) oxide or FeO, is a black powder that occurs naturally as a mineral. It is formed when iron reacts with oxygen in a low-oxygen environment. Ferrous oxide is commonly used in various applications, including as a pigment in ceramics and glass, and as a precursor for other iron compounds. In addition to its industrial uses, ferrous oxide plays a role in the production of steel and other alloys. It can also be found in some types of rust, where it contributes to the corrosion process of iron and steel materials.