Kamacite
| Kamacite | |
|---|---|
 |
|
| General and classification | |
| other names |
Beam iron |
| chemical formula | α- (Fe, Ni) |
|
Mineral class (and possibly department) |
Elements - metals, alloys, intermetallic compounds |
|
System no. to Strunz and to Dana |
1.AE.05 to 2001, discredited since 2006 ( 8th edition : I / A.07) 01.01.11.01 |
| Similar minerals | Taenit |
| Crystallographic Data | |
| Crystal system | cubic |
| Crystal class ; symbol | cubic hexakisoctahedral; 4 / m 3 2 / m |
| Space group | In 3 m (No. 229) |
| Lattice parameters | a = 2.87 to 2.88 Å |
| Formula units | Z = 2 |
| Frequent crystal faces | {111} |
| Physical Properties | |
| Mohs hardness | 4th |
| Density (g / cm 3 ) | 7.9 |
| Cleavage | indistinct |
| Break ; Tenacity | hooked |
| colour | black, gray |
| Line color | Gray |
| transparency | opaque |
| shine | Metallic luster |
| magnetism | magnetic |
| Other properties | |
| Chemical behavior | soluble in acids |
Kamacite , also known as beam iron , is a nickel-containing variety of iron of meteoritic origin. Kamacite was regarded as an independent mineral until 2006 , but was then discredited by the International Mineralogical Association (IMA) and reduced to the status of an iron variety.
Kamacite has a nickel content of 4 to 7.5%, crystallizes in the cubic crystal system with a body-centered cubic crystal structure and develops tabular crystals in black to gray color in iron meteorites , which are surrounded by light-colored, lamellar, nickel-rich taenite . These crystals can be viewed particularly well in cross-section on polished meteorite samples, where they appear bar-shaped and, together with taenite, form so-called Widmannstättensche figures . Kamacite occurs in mm-sized, irregular crystals also in all chondrites .
With a proportion of 20 to 50% nickel in the compound, taenite is formed , which has a different crystal structure. With a Ni content of 50%, tetrataenite is formed . A fine intergrowth of kamacite and taenite is called plessite .
Etymology and history
The mineral names Kamacit (beam iron ), Taenit (band iron) and Plessit (filler iron ) were coined by Karl von Reichenbach in 1861. The word Kamacit is derived from the Greek κάμαξ kamaks , which means “latte”, “stick”, “cone” and is due to the bar-shaped formation that is visible in the bevel.
classification
In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the kamacite belonged to the mineral class of the "elements" and there to the department of "metals and intermetallic alloys (without semimetals)", where together with iron , manganese and wairauite the "Iron series" with the system no. I / A.07 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), placed the kamacite in the "Metals and Intermetallic Compounds" department until 2005 and in the "Iron Kamacite Group" there the system no. 1.AE.05 within the subdivision of the "iron-chromium family". However, since Kamacite has lost its mineral status since 2006, it is no longer listed in the current Strunz system .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , still assigns the Kamacit to the class of "elements" and there in the department of the same name. Here it is together with iron, taenite , tetrataenite , Awaruit , Nickel and Wairauit in the " iron-nickel group " with the system no. 01.01.11 to be found within the sub-section "01.01 Elements: metallic elements other than the platinum group".
Education and Locations
Kamacite forms in iron meteorites in the solid state with very slow cooling according to the Fe-Ni phase diagram at temperatures between 750 and 450 ° C from taenite . It is found at the impact sites of iron meteorites on Earth. In addition, it forms when cohenite decays , which is only considered stable at high pressure.
Crystal structure
Kamacite crystallizes cubically in the space group Im 3 m (space group no. 229) with the lattice parameter a = 2.87 to 2.88 Å and 2 formula units per unit cell .
See also
literature
- Martin Okrusch, Siegfried Matthes: Mineralogy: An introduction to special mineralogy, petrology and deposit science . 7th edition. Springer Verlag, Berlin / Heidelberg / New York 2005, ISBN 3-540-23812-3 , pp. 23, 444-445 .
Web links
Individual evidence
- ↑ a b c d Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 41 .
- ↑ Ernst AJ Burke: A mass discreditation of GQN Minerals. In: Canadian Mineralogist. 44, 2006, pp. 1575-1560. (English, PDF 116.2 kB)
- ^ Vagn F. Buchwald: Handbook of Iron Meteorites. University of California Press, 1975.
- ^ John G. Burke: Cosmic Debris, Meteorites in History. University of California Press, 1986.
- ↑ 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 .