FeO, or iron(II) oxide, is a chemical compound made up of iron and oxygen. It consists of one iron atom and one oxygen atom, giving it the formula FeO. This compound is typically found in nature as a mineral called wüstite, which is formed under high-temperature conditions. FeO is known for its magnetic properties and is often used in various industrial applications, including the production of iron and steel. In terms of its appearance, FeO is usually a black or dark gray solid. It can react with acids to produce hydrogen gas and iron salts. Additionally, FeO can be oxidized to form Fe2O3, or iron(III) oxide, which is a more stable form of iron oxide commonly found in rust.