Wüstite
| Wüstite | |
|---|---|
| General | |
| Category | Oxide mineral |
| Formula | FeO |
| IMA symbol | Wüs |
| Strunz classification | 4.AB.25 |
| Crystal system | Cubic |
| Crystal class | Hexoctahedral (m3m) H–M symbol: (4/m 3 2/m) |
| Space group | Fm3m (no. 225) |
| Identification | |
| Color | Greyish white to yellow or brown; colorless in thin section |
| Crystal habit | Pyramidic, prismatic |
| Cleavage | {001} perfect |
| Fracture | Subconchoidal to rough |
| Mohs scale hardness | 5–5.5 |
| Specific gravity | 5.88 |
| Density | 5.7 g/cm3 |
| Refractive index | 1.735–2.32 in synthetic crystals |
| Pleochroism | None |
| Solubility | Soluble in dilute HCl |
| Other characteristics | Forms solid solution with periclase |
Wüstite (FeO, sometimes also written as Fe0.95O) is a mineral form of mostly iron(II) oxide found with meteorites and native iron. It has a grey colour 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 after 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 its type locality in Germany, it has been reported from Disko Island, Greenland; the Jharia coalfield, Jharkhand, India; and as inclusions in diamonds in a number of kimberlite pipes. It also is reported from deep sea manganese nodules.
Its presence indicates a highly reducing environment.