[meteorite-list] Alien Metal = tetrataenite

[bernd.pauli at paulinet.de]

"The Estherville meteorite is composed of iron, nickel, 
 phosphorous, sulfur, and some unknown alien metal."


Hello All,

This probably refers to the presence of tetrataenite (ordered FeNi) in the
Estherville mesosiderite. Tetrataenite has been observed in chondrites, iron
meteorites, and also in stony-irons. Tetrataenite has about 48-55 wt% Ni and
is unknown as a terrestrial mineral.

COLLINSON D.W. (1991) Magnetic properties of the Estherville mesosiderite

(Meteoritics 26-1, 1991, 001-010):

It is formed during the development of intergrowths of kamacite and taenite lamellae
as a nickel-iron mixture cools slowly from a high temperature to below the tetrataenite
ordering temperature of about 320°C. The nickel content across the taenite lamellae
increases sharply from their centres to the interface with kamacite. This is where the
tetrataenite, usually containing ca. 48-55% Ni, forms. Tetrataenite also occurs as rims
on taenite particles, as µm-sized grains in "cloudy" taenite, and as particles, typically
5-50µm in size, in contact with other mineral particles.


Some meteorites in which tetrataenite has been observed:

Alatage - Albion - Bawku - Campos Sales - Chaunskij - Dahmani - Estherville - Fuc Bin
Dhofar 735 (CM2 - Ni up to 60 wt% !) - Greenwell Springs - Julesburg - Leedey - Linum
Melnikovo - Rio do Pires - Saint-Séverin - Santa Catharina - Sheyang - Trenzano - Yafa
Tuxtuac - Vaca Muerta - Zaoyang


Tetrataenitically yours,

Bernd