Taenite
The nickel-rich form of iron-nickel metal in meteorites, often seen as thin bright ribbons in etched irons.
Taenite is the nickel-rich partner of kamacite. It typically contains from about 20 to over 50 per cent nickel and has a face-centred cubic crystal structure, the arrangement iron takes at high temperatures. Its name comes from a Greek word for ribbon, which suits the thin, shiny strips it forms in iron meteorites.
When a meteorite's metal was hot, it was all taenite. During slow cooling, kamacite grew out of it and nickel piled up in the shrinking taenite that remained, so taenite often shows a nickel gradient, high at its edges and lower in the middle. Measuring these profiles with a microprobe lets scientists calculate cooling rates in degrees per million years. Taenite ribbons outline the Widmanstätten pattern in octahedrites such as Gibeon and Henbury. In nickel-rich ataxites like Hoba, taenite and fine intergrowths dominate.
On an etched surface, taenite stands out as bright, mirror-like lines that resist the acid, framing the duller kamacite bands. Where the space between ribbons is filled with a fine mixture, that material is plessite. Taenite is magnetic and generally more resistant to rust than kamacite.
Related terms
Level: Enthusiast Teens and adults