Tetrataenite Locality: Nuevo Mercurio, Zacatecas , Mexico ( Locality at mindat.org ) Size: 2.7 x 2.0 x 2.0 cm. Tetrataenite is an ULTRA-RARE, EXTRATERRESTRIAL iron nickel alloy, found ONLY meteorites. On the evening of December 15, 1978 a bright fireball was observed traveling over North Central Mexico. It exploded, raining down hundreds of small black stony meteorites into the desert and ranches near the small town of Nuevo Mercurio, Zacatecas. It is classified as an H5 chondrite and the sawed slab is VERY RICH in silvery-bright tetrataenite crystals. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Tetrataenite
Ordered iron-nickel alloy of meteorites — tetragonal cousin of disordered taenite, noted for extreme magnetism.
Intro adapted from Wikipedia (CC BY-SA).
Tetrataenite is an IMA-recognized mineral species in the native element class, with the chemical formula FeNi.
It crystallizes in the tetragonal crystal system (space group Pm).
Key properties: Metallic. Anisotropism: Distinct on well-polished surfaces, bluish green to brownish orange (oil immersion). R1-R2: n.d luster.
IMA symbol Ttae, IMA status: approved, named in 1979.
Found in slowly cooled meteorites, by the ordering of Fe and Ni atoms in taenite. It is most abundant in mesosiderites and chondrites. In a serpentinized, ophiolite-hosted.
It is found associated with Kamacite, troilite, taenite (meteorites); chamosite, magnetite, chromite, Cr-Al spinel (terrestrial).
In allusion to the symmetry of the mineral, and the genetic link to taenite.