taenite

taenite

      nickel-iron mineral having a face-centred cubic structure and playing a major role in the crystallization and structure of iron meteorites and stony iron meteorites. It is sometimes referred to as γ iron, after one of the three temperature-dependent forms (allotropes) of pure iron, because the taenite is stabilized in the same face-centred cubic structure as γ iron. In the system of nickel-iron metal solutions, taenite is the only stable mineral at temperatures above 900 °C (1,650 °F). Below 900 °C the meteoritic mineral kamacite, whose nickel content is less than 7 percent by weight, separates from taenite. If the bulk composition of the nickel-iron system contains less than about 7 percent nickel by weight and the system maintains equilibrium down to low temperatures, all the taenite transforms to kamacite. If the system contains between 7 and 40 percent nickel (as is the case for all but one iron or stony iron meteorite), taenite remains stable down to a temperature of about 400 °C (750 °F), although its nickel content increases with falling temperature as the low-nickel kamacite separates from it. The separation of kamacite from taenite, aided by small amounts of phosphorus, is the process that produces the Widmanstätten pattern in iron and stony iron meteorites. Continued separation of kamacite below 400 °C results in taenite with a nickel content of as much as 52 percent by weight. At such high nickel content and temperatures below 300 °C (570 °F), the distribution of iron and nickel in the crystal structure can be highly ordered, in which case the mineral is called tetrataenite. Almost all taenite in meteorites has broken down, albeit often on a microscopic scale, to kamacite and tetrataenite.

Conel M.O'D. Alexander
 

* * *


Universalium. 2010.

Look at other dictionaries:

  • Taenite — (Fe,Ni) is a mineral found naturally on Earth mostly in iron meteorites. It is an alloy of iron and nickel, with nickel proportions of 20% up to 65%. It is opaque with a metallic grayish to white color. The structure is isometric hexoctahedral.… …   Wikipedia

  • taenite — noun A mineral, found in certain meteorites, that is a magnetic alloy of iron and nickel …   Wiktionary

  • taenite — tae·nite …   English syllables

  • taenite — ˈtēˌnīt noun ( s) Etymology: German tänit, from tän taen + it ite : a mineral consisting of a nickel iron alloy that forms with kamacite the mass of most meteoric iron …   Useful english dictionary

  • Nickel — This article is about the chemical element. For other uses, see Nickel (disambiguation). cobalt ← nickel → copper ↑ Ni ↓ Pd …   Wikipedia

  • Widmanstätten pattern — Widmanstätten patterns, called also Thomson structures, are unique figures of long nickel iron crystals, found in the octahedrite iron meteorites and some pallasites. They consist of a fine interleaving of kamacite and taenite bands or ribbons… …   Wikipedia

  • Antitaenite — is a meteoritic metal alloy mineral composed of iron and nickel, 20 40% Ni (and traces of other elements) that has a face centered cubic crystal structure. Its existence as a new mineral species occurring in both iron meteorites and in chondrites …   Wikipedia

  • Taenit — Widmannstättensche Figur schmale, helle Streifen sind Taenit Bänder Chemische Formel γ (Fe,Ni) Mineralklasse Elemente Metalle, Legierungen und intermetallische Verbindungen I/ …   Deutsch Wikipedia

  • meteorite — meteoritic /mee tee euh rit ik/, meteoritical, meteorital /mee tee euh ruyt l/, adj. /mee tee euh ruyt /, n. 1. a mass of stone or metal that has reached the earth from outer space; a fallen meteoroid. 2. a meteoroid. [1815 25; METEOR + ITE1] * * …   Universalium

  • iron meteorite —  any meteorite consisting mainly of iron, usually combined with small amounts of nickel. When such meteorites, often called irons, fall through the atmosphere, they may develop a thin, black crust of iron oxide that quickly weathers to rust.… …   Universalium

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”