Wüstite
Iron(II) oxide, found in the fusion crusts of iron meteorites and in cosmic spherules.
Key facts
- Formula
- FeO
- Family
- Oxides
- Crystal system
- Cubic
What it is
Wüstite is iron monoxide, with a rock-salt structure that always lacks a few iron atoms, so its true formula is slightly less than FeO. It is stable only at high temperature and breaks down to iron and magnetite on slow cooling. It is named after Fritz Wüst, a German metallurgist.
Where it is found
It forms in the thin fusion crust of iron meteorites, where the surface melts and oxidises during flight through the atmosphere, and in iron-rich cosmic spherules. It also occurs as a weathering and heating product on some recovered irons.
How it is recognised
It is grey in reflected light, often with tiny magnetite blebs. Its identity is confirmed by X-ray diffraction.
Did you know?
Wüstite and magnetite in fusion crust are only fractions of a millimetre thick.
Wüstite is a familiar component of the scale that forms on hot steel.