Chaoite

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Chaoite
General and classification
other names

IMA 1968-019

chemical formula C.
Mineral class
(and possibly department) 		Elements - semi-metals, non-metals
System no. to Strunz
and to Dana 		1.CB.05b ( 8th edition : I / B.02)
01.03.06.04
Crystallographic Data
Crystal system hexagonal
Crystal class ; symbol dihexagonal-dipyramidal; 6 / m  2 / m  2 / m
Space group P 6 / mmm (No. 191)Template: room group / 191
Lattice parameters a  = 8.95  Å ; c  = 14.08 Å
Formula units Z  = 168
Physical Properties
Mohs hardness 1 to 2
Density (g / cm 3 ) calculated: 3.43
Cleavage not defined
colour dark gray to black
Line color not defined
transparency opaque
shine Metallic luster

Chaoite is a very rare mineral from the mineral class of the elements . It crystallizes in the hexagonal crystal system and is a modification of carbon . The mineral develops 3–15 μm large lamellae, which are fused with graphite , of dark gray to black color and a metallic sheen .

Etymology and history

The mineral was discovered in 1968 by Ahmed El Goresy and G. Donnay in the shockwave-melted graphite gneiss of the Nördlinger Ries crater near Möttingen in Bavaria . They named it after the American-Chinese petrologist Edward Ching-Te Chao .

classification

In the old ( 8th edition ) and new systematics of minerals ( 9th edition ) according to Strunz , Chaoite is sorted into the section of "semi-metals and non-metals". However, the new system divides this even further. Chaoite now belongs to the “carbon-silicon family” together with Lonsdaleit , fullerite (previously without recognition by the IMA / CNMNC), graphite , diamond and silicon .

The classification of minerals by Dana provides chaoite also with diamond, graphite, lonsdaleite and fullerite in the "carbon polymorph group" the department "Native element with semi-metallic and non-metallic elements" (translation: "Polymorphic carbon group" of Department “Solid elements with semi-metallic and non-metallic elements”).

Crystal structure

Chaoite crystallizes in the hexagonal crystal system in the space group P 6 / mmm (space group no. 191) with the lattice parameters a  = 8.95  Å and c  = 14.08 Å and 168 formula units per unit cell . Template: room group / 191

Education and Locations

Chaoite is formed by shock metamorphosis in graphitic gneiss and meteorites . It is associated with graphite, zirconium , rutile , pseudobrookite , magnetite , nickel- pyrrhotite and baddeleyite .

So far, only six locations of the mineral are known (as of 2018). In addition to the type locality near Möttingen, chaoite was found in the Nördlinger Ries near Bopfingen as well as in the meteorites Goalpara (Assam) and Dyalpur (Uttar Pradesh) in India , in the Popigai crater in Siberia (Russia) and in the Haverö meteorite near Nagu ( Nauvo ) in Finnland.

See also

List of minerals

literature

  • Ahmed El Gorsey: A new carbon modification from the Nördlinger Ries . In: Natural Sciences . tape 56 , 1969, p. 493–494 ( available online at vdocuments.mx ).

Web links

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.  51 .
  2. ↑ a b c d Chaoite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 (English, handbookofmineralogy.org [PDF; 56  kB ; accessed on December 28, 2018]).
  3. ↑ a b Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties. Status 03/2018 . 7th, completely revised and supplemented edition. Weise, Munich 2018, ISBN 978-3-921656-83-9 .
  4. ↑ Ahmed El Goresy, G. Donnay: A New Allotropic Form of Carbon from the Ries Crater . In: Science . tape 161 , 1968, pp. 363–364 , doi : 10.1126 / science.161.3839.363 (English).
  5. ↑ Find location list for Chaoite at the Mineralienatlas and at Mindat