Wustite



Chemical formula: FeO
Melting point: 1370oC
Density: 5.745 g/cm3
Microhardnes: No data
Hardness (Moh's): 5-5.5
Luminescence: No data
Colour in air, bright field reflection: Middle grey
Colour, polarized reflection: No data
Shape: Rounded off, smooth
Crystal system: Cubic
Cell dimensions: a=4.296 A
PDF number: 00-002-1180
ICSD number: Data not found
Note: Wustite is only stable above 560oC (stability range 560-1370oC) and decomposes to alpha-iron and Fe3O4, bellow this temperature. During rapid cooling this transformation take place only partially or not all and therefore wustite can also exist at room temperature. Wustite with magnetite in indogenous silicate steel inclusions often forms a dendritic structure, similar to that of manganosite. Wustite inclusions (with magnetite), a product from iron oxidation, are often found bellow the surface of solidified steel cast from the top. Multiphase oxide inclusions with wustite tigether with the other iron oxides are frequently observed in or around surface cracks or places where the steel surface has been oxidized. Such wustite inclusions also often have varying amounts of MnO in solid solution. It is sometimes difficult to distinguish between wustite and magnetite, which are both cubic and often grow in close contact, but etching with 4% Nital, gives darker colour for the wustite phase.

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