Tongbait

from Wikipedia, the free encyclopedia
Tongbait
General and classification
other names

IMA 1982-003

chemical formula Cr 3 C 2
Mineral class
(and possibly department) 		elements
System no. to Strunz
and to Dana 		1.BA.15
01.01.17.01
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol orthorhombic-dipyramidal; 2 / m  2 / m  2 / m
Space group Pnma (No. 62)Template: room group / 62
Lattice parameters a  = 5.5399 (6)  Å ; b  = 2.8327 (4) Å; c  = 11.494 Å
Formula units Z  = 4
Physical Properties
Mohs hardness 8.5 ( VHN 100 = 1885)
Density (g / cm 3 ) measured: not defined; calculated: 6.64
Cleavage not defined
Break ; Tenacity brittle
colour brownish yellow; in Auflich light purple
Line color dark gray
transparency opaque (opaque)
shine Metallic luster
Other properties
Chemical behavior not soluble in HCl , H 2 SO 4 or HNO 3

Tongbait is a very seldom occurring mineral from the mineral class of the "elements" with the chemical composition Cr 3 C 2 and thus, chemically speaking, chromium carbide .

Tongbait crystallizes in the orthorhombic crystal system and develops mostly prismatic, pseudo-hexagonal crystals up to 0.3 mm in size with occasionally spear-shaped ends. The mineral is opaque in every form and shows a strong metallic luster on the brownish-yellow surfaces, which also appear light purple in incident light .

With a Mohs hardness of 8.5, Tongbait is one of the hard minerals and its hardness lies between the reference minerals topaz (hardness 8) and corundum (hardness 9) on a scale of up to 10.

Etymology and history

Tongbait was first discovered near the village of Liu Zhuang in Tongbai County in the south of the Chinese province of Henan . The first description was in 1983 by Tian Peixue, Fang Qingsong, Chen Keqiao and Peng Zhizhong, who named the mineral after its type locality .

A storage location for the type material of the mineral is not known or has not been defined.

classification

Since the tongbait was only discovered in 1982 and recognized as an independent mineral, it is not listed in the outdated 8th edition of the mineral classification according to Strunz . Only in the “Lapis Mineral Directory”, which was last updated in 2018, which, out of consideration for private collectors and institutional collections, is still based on the classic system of Karl Hugo Strunz , the mineral received the system and mineral number. I / A.09-30 . In the "Lapis system", Tongbait belongs to the department "Carbides, Nitrides, Phosphides and Silicides (metal-like compounds)".

The 9th edition of Strunz's mineral systematics, which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), assigns the tongbait to the class of "elements" and there to the department of "metallic carbon, nitrogen and phosphorus compounds". This is further subdivided according to the type of compound, so that the mineral can be found according to its composition in the sub-section “Carbide”, where it is the only member of the unnamed group 1.BA.15 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the tongbait to the class and there in the department of the same name of "elements". Here it can be found together with Florenskyit and Andreyivanovite in the unnamed group 01.01.17 within the sub-section "Elements: Metallic elements other than the platinum group".

Chemism

The analysis of four Tongbait samples showed an average composition of 84.26 wt .-% chromium (Cr), 13.37 wt .-% carbon (C), 1.18 wt .-% iron (Fe) and 1, 25 wt% nickel (Ni). On the basis of two carbon atoms, the empirical formula (Cr 2.906 Fe 0.036 Ni 0.036 ) Σ = 2.978 C 2 was derived and idealized to Cr 3 C 2 .

Crystal structure

Tongbait crystallizes orthorhombically in the space group Pnam (space group no. 62, position 6) with the lattice parameters a  = 5.5399 (6)  Å ; b  = 2.8327 (4) Å and c  = 11.494 Å as well as four formula units per unit cell . Template: room group / 62.6

Six chromium atoms each form trigonal prisms in the crystal structure , with the prisms partially covered by one to three Cr atoms on the surfaces. The carbon atoms are embedded in the center of these prisms .

Crystal structure of tongbait

  • with viewing direction parallel to the c-axis
    (out of the picture)

  • looking parallel to the a-axis

  • looking parallel to the b-axis

  • with viewing direction parallel to the c-axis
    (into the picture)

  • spatial representation in the standard crystallographic orientation

Color table: __ Cr     __ C

Education and Locations

Tongbait formed in ultramafic rocks and was found at its type locality near the village of Liu Zhuang in Tongbai County in China, together with a whole range of accompanying minerals such as the native elements lead , chromium , iron , gold , copper and platinum, as well as element minerals Awaruit , the sulphides altaite , bismuth hauchecornite , chalcopyrite , cubanite , pentlandite , pyrite , pyrrhotite and violarite , the oxides magnesiochromite , magnetite , ilmenite and the silicates apatite , diopside , enstatite , forsterite , hydrogrossular and phlogopite .

The hitherto only other known location (as of 2019) is a platinum - gold - deposit at the river Is in circles Isowsk in the Russian Sverdlovsk Oblast (Ural), where Tongbait together with the first discovered there Isovit and Cinnabar , chromite and various platinum group minerals has been discovered.

See also

literature

  • Stig Rundqvist, Gunilla Runnsjö: Crystal structure refinement of Cr 3 C 2 . In: Acta Chemica Scandinavica . tape 23 , 1969, p. 1191–1199 (English, actachemscand.org [PDF; 926 kB ; accessed on February 9, 2019]).
  • Tian Peixue, Fang Qingsong, Chen Keqiao, Peng Zhizhong: A study on tongbaite - A new mineral . In: Acta Mineralogica Sinica . tape 3 , no. 4 , 1983, p. 241–245 (Chinese with a brief description in English).
  • Pete J. Dunn, George Y. Chao, Michael Fleischer, James A Ferraiolo, Richard H. Langley, Adolf Pabst, Janet A. Zilczer: New Mineral Names . In: American Mineralogist . tape 70 , no. 1-2 , 1985, pp. 214–221 (English, minsocam.org [PDF; 937 kB ; accessed on February 8, 2019]).
  • 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. 47 (English).

Web links

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

Individual evidence

  1. ^ IMA / CNMNC List of Mineral Names; November 2018 (English, PDF 1.7 MB)
  2. ↑ a b c d e Jochen Glaser, Ruth Schmitt and H.-Jürgen Meyer: New structure refinement and properties of Cr 3 C 2 . In: Journal of Nature Research B . tape 58 , no. 9 , 2003, p. 929-933 , doi : 10.1515 / znb-2003-0916 ( znaturforsch.com [PDF; 281 kB ; accessed on February 8, 2019]).
  3. ^ David Barthelmy: Tongbaite Mineral Data. In: webmineral.com. Retrieved February 7, 2019 .
  4. ↑ a b c d e f Tongbaite . 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; 68  kB ; accessed on February 7, 2019]).
  5. ↑ a b c d Pete J. Dunn, George Y. Chao, Michael Fleischer, James A Ferraiolo, Richard H. Langley, Adolf Pabst, Janet A. Zilczer: New Mineral Names . In: American Mineralogist . tape 70 , no. 1-2 , 1985, pp. 218 (English, minsocam.org [PDF; 937 kB ; accessed on February 8, 2019]).
  6. ↑ 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 .
  7. ↑ Find location list for Tongbait at the Mineralienatlas and at Mindat
  8. ^ Igor V Pekov: New minerals from former Soviet Union countries, 1998-2006: New minerals approved by the IMA commission on new minerals and mineral names . In: Mineralogical Almanac . tape 11 , 2007, p. 26 (English, rruff.info [PDF; 3.9 MB ; accessed on February 11, 2019]).