The octahedrites are the most common group of nickel - iron meteorites . They consist of the minerals kamacite and taenite . If the surface of these meteorites is polished and etched, the typical Widmanstatt structures appear . They consist of kamacite beams separated from taenite by thin slats. In the third dimension, the kamacite is in plates that are arranged parallel to the faces of an octahedron, hence the name octahedron.
The octahedrites are further subdivided into structural classes according to the width of the kamacite bars (there is a connection with the nickel content):
- Coarsest octahedrites, more than 3.3 mm, 5–9% Ni
- Coarse octahedrites, 1.3-3.3mm, 6.5-8.5% Ni
- Medium octahedrites, 0.5 to 1.3 mm, 7-13% Ni
- Fine octahedrites, 0.2-0.5mm, 7.5-13% Ni
- Finest octahedrites, smaller than 0.2 mm, 17–18% Ni
They can also be divided into chemical groups I to IV according to their content of nickel and the trace elements germanium , gallium and iridium . There are also a number of octahedrites that have not yet been assigned to any of these groups and that are therefore referred to as abnormal .
Well-known representatives of the octahedrite group are the Gibeon meteorite , Sikhote-Alin meteorite , Campo-del-Cielo meteorite , Canon Diablo meteorite , Morasko meteorite , Nantan meteorite , the Toluca and the Cranbourne meteorites .
- Vagn F. Buchwald, Handbook of Iron Meteorites, Univ. of California Press, 1975
- John. T. Wasson, Meteorites, Springer-Verlag 1974.