Taenit

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Taenit
Gibeon meteorite, pattern.jpg
Close-up of the Gibeon neteorite (Namibia) with Widmannstättenscher figure
narrow, light stripes (easily recognizable in the lower half of the picture) are Taenite bands
General and classification
chemical formula γ- (Fe, Ni)
Mineral class
(and possibly department) 		Elements - metals, alloys and intermetallic compounds
System no. to Strunz
and to Dana 		1.AE.10 ( 8th edition : I / A.08)
01.01.11.02
Similar minerals Kamacite
Crystallographic Data
Crystal system cubic
Crystal class ; symbol cubic hexakisoctahedral; 4 / m  3  2 / m
Space group Fm 3 m (No. 225)Template: room group / 225
Lattice parameters a  = 3.60  Å
Formula units Z  = 4
Physical Properties
Mohs hardness 5 to 5.5
Density (g / cm 3 ) measured: 7.8 to 8.22; calculated: 8.29
Cleavage no
colour silver-white to gray-white
Line color light gray
transparency opaque
shine Metallic luster
magnetism strong magnetic

Taenite ( iron band ) is a rather rare mineral from the mineral class of the "elements". It crystallizes in the cubic crystal system with the chemical composition γ- (Fe, Ni), so it is an alloy of nickel and iron with a face-centered cubic crystal structure .

Taenite is opaque and develops narrow, ribbon-shaped crystals of silver or gray-white color and metallic sheen .

So far, natural taenite has only been found as a component of iron-nickel meteorites . This cosmically created taenite has a nickel content of around 30 to 50%.

With a proportion of 4 to 7.5% nickel in the compound, kamacite forms with a different crystal structure, with a proportion of> 50% tetrataenite is formed . A fine-grained intergrowth of kamacite and taenite is called plessite .

Etymology and history

The name Taenit is derived from the Greek ταινία [tainia] for band , because Taenit appears in this form in the Widmanstätten structures of iron meteorites. The name was coined by Karl von Reichenbach in 1861 , along with the names for Kamacit and Plessit .

The Gorge River on the South Island of New Zealand is considered the type locality for Taenit as well as the related Awaruit (Ni 3 Fe) .

classification

In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the Taenit belonged to the department of " Metals and intermetallic alloys (without semimetals )", where, together with Awaruit , Jedwabit , Nickel and Tetrataenit, it was part of the "Nickel series" the system no. I / A.08 formed.

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also classifies the Taenit in the department of "Metals and Intermetallic Compounds". This is, however, further subdivided into element families with similar properties, so that the mineral can be found according to its composition in the sub-section "iron-chromium family", where it is only together with tetrataenite the "taenite group" with system no. 1.AE.10 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Taenit to the class of "elements" and there to the department of the same name. Here it is in the " iron-nickel group " with system no. 01.01.11 to be found in the subsection "Elements: metallic elements other than the platinum group".

Crystal structure

Taenite crystallizes cubically in the space group Fm 3 m (space group no. 225) with the lattice parameter a  = 3.60  Å and 4 formula units per unit cell . Template: room group / 225

properties

Taenit is very magnetic .

Its Mohs hardness of 5 to 5.5 corresponds to that of the reference mineral apatite or the artificial stone rhinestone and can therefore still be scratched with a pocket knife .

Education and Locations

Micrograph of the “Cape York” meteorite (Greenland). The black, irregular grains are made of Troilite , surrounded by a narrow band of Schreiberite and embedded in a Widmanstaette structure of Kamacite and Taenite

Taenite is a natural alloy of face-centered cubic γ- iron and nickel , with a higher nickel content than Kamacite. Taenite crystallizes from an Fe, Ni melt between about 1400 and 900 ° C (depending on the nickel content). With further cooling, Kamacite that is poor in nickel is formed in the solid state, with the nickel content in the taenite increasing.

In the so-called Widmanstätten structure , which is visible on grinded , polished and etched octahedrites , the taenite crystals can be seen as bright, shiny, thin bands between the dark kamacite bars.

Taenite occurs in all octahedrites, the most common class of iron meteorites . Also in the Fe, Ni grains of the chondrites , almost always grown together with Kamacite. A total of around 150 meteorites are known so far (as of 2013) in which Taenite could be detected.

The following meteorites are examples:

Taenite was also found in rock samples that the " Apollo 16 " mission brought from the moon .

See also

literature

Web links

Commons : Taenite  - collection of images, videos and audio files

Individual evidence

  1. ^ A b c Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  41 .
  2. ↑ a b Taenite. In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America. 2001 ( handbookofmineralogy.org PDF 55.7 kB).
  3. ^ Helmut Schrätze , Karl-Ludwig Weiner : Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp.  77 .
  4. ^ Karl von Reichenbach : About the inner structure of the closer components of the meteor iron. In: Poggendorff's annals of physics and chemistry. Volume 114, 1861, p. 1861.
  5. ↑ Hans Lüschen: The names of the stones. The mineral kingdom in the mirror of language . 2nd Edition. Ott Verlag, Thun 1979, ISBN 3-7225-6265-1 , p. 275 .
  6. ^ Mindat - type locality Gorge river, South Island, New Zealand.
  7. ^ Vagn Fabritius Buchwald: Handbook of Iron Meteorites . University of California Press, 1975, ISBN 0-520-02934-8 .
  8. ^ Fritz Heide, F. Wlotzka: Small meteorite science . Springer, Berlin [a. a.] 1988, ISBN 3-540-19140-2 .
  9. ↑ Mindat - Number of localities for Taenite.
  10. ↑ a b List of localities for Taenite in the Mineralienatlas and Mindat .