Wüstite (Fe) is a mineral form of iron(II) oxide and native iron. It has a gray color with a greenish tint in reflected light. Wüstite crystallizes in the isometric-hexoctahedral crystal system in opaque to translucent metallic grains. It has a Mohs hardness of 5 to 5.5 and a specific gravity of 5.88. Wüstite is a typical example of a non-stoichiometric compound.
Wüstite was named for Fritz Wüst (1860–1938), a German metallurgist and founding director of the Kaiser-Wilhelm-Institut für Eisenforschung (presently Max Planck Institute for Iron Research GmbH
In addition to the type locality in Germany, it has been reported from Disko Island coalfield, Jharkhand in a number of kimberlite pipes. It also is reported from deep sea manganese nodules.
Its presence indicates a highly reducing environment.