Lonsdaleit
| Lonsdaleit | |
|---|---|
 |
|
| General and classification | |
| other names |
IMA 1966-044 |
| chemical formula | β'-C |
|
Mineral class (and possibly department) |
Elements - semi-metals, non-metals |
|
System no. to Strunz and to Dana |
1.CB.10b ( 8th edition : I / B.02) 01.03.06.03 |
| Crystallographic Data | |
| Crystal system | hexagonal |
| Crystal class ; symbol | dihexagonal-dipyramidal; 6 / m 2 / m 2 / m |
| Space group | P 6 3 / mmc (No. 194) |
| Lattice parameters | a = 2.52 Å ; c = 4.12 Å |
| Formula units | Z = 4 |
| Physical Properties | |
| Mohs hardness | 7 to 8 |
| Density (g / cm 3 ) | 3.3 to 3.52 |
| Cleavage | perfectly |
| colour | yellow-brown, brown-black |
| Line color | brownish yellow |
| transparency | translucent to opaque |
| shine | Please complete |
| Crystal optics | |
| Refractive indices |
n ω = 2.404 n ε = 2.404 |
| Birefringence | δ = 2.404 |
| Optical character | uniaxial alternating |
Lonsdaleite , often referred to as hexagonal diamond , is a very rare mineral from the mineral class of the elements and a very rare modification of carbon and the high-pressure modification of diamond .
Lonsdaleit crystallizes in the hexagonal crystal system and forms fine-grain, cubic or cuboctahedral aggregates as well as polycrystalline mineral aggregates with diamond.
Etymology and history
Lonsdaleit was first found and described in 1967. It is named in honor of the Irish crystallographist and professor Kathleen Lonsdale .
classification
In the old (8th edition) and new systematics of minerals (9th edition) according to Strunz , the Lonsdaleit is sorted into the department of "semi-metals and non-metals". However, the new system divides this even further. Lonsdaleit now belongs to the "carbon-silicon family" together with chaoite , fullerite (previously without recognition by the IMA / CNMNC), graphite , diamond and silicon .
The systematics of minerals according to Dana also puts the Lonsdaleit together with diamond, graphite, chaoite and fullerite in the “Carbon Polymorph group” of the department “Native Elements with semi-metallic and non-metallic elements” (translation: “Polymorphic carbon group”) the department “Solid elements with semi-metallic and non-metallic elements” ).
Crystal structure
Lonsdaleit crystallizes in the hexagonal crystal system in the space group P 6 3 / mmc (space group no. 194) with the lattice parameters a = 2.52 Å and c = 4.12 Å and four formula units per unit cell .
Education and Locations
Lonsdaleit is formed when graphite is converted into a diamond-like structure by shock events, i.e. at high pressure and high temperature , but the hexagonal crystal lattice of the graphite is retained. Such conditions prevail, for example, in the event of impacts on the meteorite parent body. Measurements on shock-compressed graphite with instantaneous determination of the structure by X-ray diffraction confirm this view.
The type locality for the mineral is the area surrounding the Barringer crater and the Canyon Diablo meteorite found there. Other sites are the iron meteorite Allan Hills 77283, the Ureilite Kenna, and a kimberlite field in China . Lonsdaleite is increasingly found together with graphite and diamond in Ureilites , a subspecies of the Achondrites .
See also
literature
- Helmut Schrätze , Karl-Ludwig Weiner : Mineralogy. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 95, 100 .
- Lonsdaleite . 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; 57 kB ; accessed on December 7, 2017]).
Web links
- Mineral Atlas: Lonsdaleit (Wiki)
- American-Mineralogist-Crystal-Structure-Database - Lonsdaleite (English)
Individual evidence
- ^ A b Helmut Schrätze , Karl-Ludwig Weiner : Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 100 .
- ↑ a b c FP Bundy: Hexagonal Diamond - New Form of Carbon . In: The Journal of Chemical Physics . tape 46 , 1967, p. 3437 , doi : 10.1063 / 1.1841236 .
- ↑ a b c d Mindat - Lonsdaleite (English)
- ↑ Webmineral - Lonsdaleite (English)
- ↑ Clifford Frondel, Ursula B. Marvin: Lonsdaleite, a Hexagonal Polymorph of Diamond . In: Nature . tape 214 , 1967, pp. 587-589 , doi : 10.1038 / 214587a0 .
- ↑ a b Martin Okrusch, Siegfried Matthes: Mineralogie. An introduction to special mineralogy, petrology and geology . 7th, completely revised and updated edition. Springer, Berlin [a. a.] 2005, ISBN 3-540-23812-3 , pp. 27, 441 .
- ↑ D. Kraus, A. Ravasio, M. Gauthier, DO Gericke, J. Vorberger, S. Frydrych, J. Helfrich, LB Fletcher, G. Schaumann, B. Nagler, B. Barbrel, B. Bachmann, EJ Gamboa, S. Göde, E. Granados, G. Gregori, HJ Lee, P. Neumayer, W. Schumaker, T. Döppner, RW Falcone, SH Glenzer, M. Roth: Nanosecond formation of diamond and lonsdaleite by shock compression of graphite . In: Nature Communications . tape 7 , March 14, 2016, doi : 10.1038 / ncomms10970 ( nature.com [accessed December 7, 2017]).
- ^ Roy S. Clarke, Daniel E. Appleman, Daphne R. Ross: An Antarctic iron meteorite contains preterrestrial impact-produced diamond and lonsdaleite . In: Nature . tape 291 , 1981, pp. 396-398 , doi : 10.1038 / 291396a0 .