Taenite
Nickel-rich iron metal, which forms the thin bright ribbons of the Widmanstätten pattern.
Key facts
- Formula
- γ-(Fe,Ni), about 20–50% nickel
- Family
- Metals and alloys
- Crystal system
- Cubic
What it is
Taenite is iron–nickel metal with a face-centred cubic structure, the high-temperature form of nickel-iron. Its name comes from the Greek for band or ribbon. As a metal core cools, nickel moves from growing kamacite into the remaining taenite, so taenite ends up richer in nickel, especially at its edges.
Where it is found
It forms the narrow, shiny ribbons between kamacite bands in octahedrites, and makes up most of the nickel-rich irons called ataxites. It is common in ordinary chondrite metal grains and in pallasites and mesosiderites.
How it is recognised
On an etched surface taenite is bright and stands slightly proud, because it resists acid better than kamacite. Its nickel content rises towards the edges of each ribbon, giving an M-shaped profile when measured across it.
Did you know?
The M-shaped nickel profile across a taenite ribbon is one of the best ways to measure the cooling rate of an asteroid core.
Taenite is not attracted to a magnet as strongly as kamacite.