Akaganéite is an iron(III) oxide-hydroxide / chloride mineral with formula: Fe³⁺O(OH,Cl) e.g.; β-FeO(OH). It is formed by the weathering of pyrrhotite (Fe_1-xS). Nickel also has been reported in the structure. It has a monoclinic crystal structure, a metallic luster and a brownish yellow streak. It is named after the Akagane mine in Iwate, Japan, in which it was discovered. It has also been found in widely dispersed locations around the world and in rocks from the Moon that were brought back during the Apollo Project. The occurrences in meteorites and the lunar sample are thought to have been produced by interaction with Earth's atmosphere.