Kamacite
Low-nickel iron metal, the main mineral of most iron meteorites and the metal flecks in chondrites.
Key facts
- Formula
- α-(Fe,Ni), about 5–7.5% nickel
- Family
- Metals and alloys
- Crystal system
- Cubic
What it is
Kamacite is iron metal containing a few per cent nickel, with a body-centred cubic structure. Its name comes from the Greek for a pole or beam, after the bands it forms. As a nickel-iron mass cools slowly, kamacite grows as plates within high-temperature taenite, producing the Widmanstätten pattern.
Where it is found
It is the main mineral of hexahedrites, made almost entirely of kamacite, and of octahedrites, in which it forms the broad bands of the Widmanstätten pattern. It also makes up most of the metal grains in ordinary chondrites and occurs in pallasites, mesosiderites and enstatite meteorites. It contains a little cobalt, whose amount helps classify chondrites.
How it is recognised
It is silvery grey and strongly magnetic. On an etched surface it forms the wider, slightly darker, frosted bands, sometimes crossed by fine Neumann lines made by shock.
Did you know?
The width of kamacite bands shows how fast an asteroid's core cooled, often only a few degrees every million years.
Kamacite in chondrites is the reason a magnet sticks to most stony meteorites.