Taenite
Taenite ( strip) is a rarely occurring mineral from the mineral class of " elements ". It crystallizes in the cubic crystal system with the chemical composition of γ - (Fe, Ni), and is therefore an alloy of nickel and iron with a face-centered cubic crystal structure.
Taenite is opaque and developed narrow, ribbon-like crystals of silver - gray or white color and metallic luster.
Natural taenite has so far been found only as a component of iron-nickel meteorites. This cosmic resulting taenite has a nickel content of about 30 to 50%.
If the ratio from 4 to 7.5 % of nickel in the compound is kamacite forms with another crystal structure, at a level of > 50% is produced Tetrataenite. A fine-grained intergrowth of kamacite and taenite is called Plessit.
Special Features
Taenite is strongly magnetic.
Its Mohs hardness from 5 to 5.5 corresponds to that of the reference mineral apatite or artificial stone rhinestone and can still be scratched with a penknife therefore.
Etymology and history
The name taenite is derived from the Greek ταινία [ tainia ] for band because taenite appears in this form in the Widmanstatten structures of iron meteorites. The name was coined in 1861 by Karl von Reichenbach, along with the names of kamacite and Plessit.
As a type locality for taenite as well as the related Awaruit ( Ni3Fe ) of the Gorge River applies in the South Island of New Zealand.
Classification
In the now outdated but still in use 8th edition of the mineral classification by Strunz the taenite belonged to the department of " metals and intermetallic alloys ( semimetals ) " where he along with Awaruit, Jedwabit, nickel and Tetrataenite the "Nickel Series" with system no. I/A.08 formed.
The 9th edition used since 2001 and valid by the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the taenite also in the department of " metals and intermetallic compounds " one. However, this is further subdivided by element families with similar characteristics, so that the mineral is found according to its composition in the subsection " iron-chromium- family " where there is only together with Tetrataenite the " Taenitgruppe " with the system no. 1.AE.10 forms.
The mainly common in English-speaking classification of minerals according to Dana assigns the taenite in the class of " elements " and then in the same department. Here he is in the " iron-nickel group " with the system no. 01:01:11 within the subdivision " elements: metallic elements other than the platinum group " to find.
Education and Locations
Taenite is a natural alloy of face-centered cubic γ - iron and nickel, with a higher nickel content than in kamacite. Taenite crystallized from a Fe, Ni- melt between about 1400 and 900 ° C (depending on the nickel content ). On further cooling, forms in the solid state nickel poorer kamacite, the nickel content increases in taenite.
In the so-called Widmanstatten structure that is visible on sanded, polished and etched octaedrite that Taenitkristalle are recognizable as bright shiny, thin strips between the dark kamacite bars.
Taenite comes in all octaedrite, the most common class of iron meteorites before. In addition, in the Fe, Ni grains of chondrites, almost always intergrown with kamacite. Overall, so far (as of 2013) about 150 meteorites are known in which taenite could be detected.
As examples, the following meteorites are:
- Gebel Kamil meteorite in Egypt
- Frontier Mountain meteorite, found in Victoria Land Antarctica
- Campo del Cielo meteorite in Argentina
- Henbury meteorite in Australia
- Santa Catarina meteorite in Brazil
- Boxian meteorite in China
- Ramsdorf meteorite in Germany (see also meteorite fall Ramsdorf )
- Abee meteorite in Canada
- Toluca meteorite in Mexico
- Morasko meteorite in Poland
- Sikhote -Alin meteorite in Siberia, Russia
- Rafrüti meteorite in Switzerland
- Canyon Diablo meteorite in Arizona, USA
Even in rock samples brought back the " Apollo 16 " mission from the moon, taenite was detected.
Crystal structure
Taenite crystallizes in cubic space group Fm3m ( Raumgruppen-Nr. 225 ) with the lattice parameters a = 3.60 Å and four formula units per unit cell.