Edgarit

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Edgarit
General and classification
other names

IMA 1995-017

chemical formula FeNb 3 S 6
Mineral class
(and possibly department) 		Sulfides and sulfosalts
System no. to Strunz
and to Dana 		2.DB.25 ( 8th edition : II / D.07)
02.11.13.01
Crystallographic Data
Crystal system hexagonal
Crystal class ; symbol hexagonal trapezoidal; 622
Space group P 6 3 22 (No. 182)Template: room group / 182
Lattice parameters a  = 5.77  Å ; c  = 12.19 Å
Formula units Z  = 2
Physical Properties
Mohs hardness not defined ( VHN 5 = 135; VHN 10 = 205)
Density (g / cm 3 ) measured: 4.98 (synthetic); calculated: 4.99
Cleavage completely after {0001}
colour bronze yellow, dark gray to black
Line color brownish gray
transparency opaque
shine Metallic luster

Edgarit is a very rarely occurring mineral from the mineral class of "sulfides and sulfosalts" with the chemical composition FeNb 3 S 6 and is therefore chemically an iron - niobium - sulfide .

Edgarit crystallizes in the hexagonal crystal system and develops mostly opaque, tabular crystals up to about 0.15 mm in size and bronze-yellow or dark gray to black in color with a metallic sheen on the surfaces. His stroke color is black.

Etymology and history

Edgarit was first discovered in 1995 at Kaskasnjuntschorr (Каскаснюнчорр, English Kaskasnyunchorr ) in the Chibinen on the Russian Kola Peninsula . The mineral was scientifically described by Andrei Y. Barkov, Robert F. Martin, Yuri P. Men'shikov, YE Savchenko, Yves Thibault and Kauko Veikko Olav Laajoki, who named it after Professor of Petrology at the University of Western Ontario Alan D. Edgar (1935–1998) named to honor his work on alkaline rocks.

The type material of the mineral is in the Royal Ontario Museum in Toronto, Canada, under the catalog no. M46177 kept.

classification

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the edgarite belonged to the mineral class of "sulfides and sulfosalts" and there to the department of "sulfides with the molar ratio metal: S, Se, Te <1: 1", where he and Paxit formed the unnamed group II / D.07 .

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 Edgarit to the division of “Metal sulfides with M: S = 3: 4 and 2: 3”. This is also further subdivided according to the exact molar ratio, so that the mineral can be found according to its composition in the sub-section "M: S = 2: 3", where it is the only member of the unnamed group 2.DB.25 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Edgarit to the class of "sulfides and sulfosalts" and there in the department of "sulfide minerals". Here he is to be found as the only member of the unnamed group 02.11.13 within the subsection “Sulphides - including selenides and tellurides - with the composition A m B n X p , with (m + n): p = 2: 3”.

Crystal structure

Edgarit crystallizes hexagonally in the space group P 6 3 22 (space group no. 182) with the lattice parameters a  = 5.77  Å and c  = 12.19 Å as well as 2 formula units per unit cell . Template: room group / 182

Education and Locations

Edgarite is formed in feldspar-rich , fenitized xenolites in foyaite . The accompanying minerals included pyrrhotite , marcasite , pyrite and alabandine .

Apart from its type locality Kaskasnjuntschorr in the Chibinen, no other location for Edgarite is known (as of 2017).

See also

literature

  • K. Anzenhofer, JM van den Berg, P. Cossee, JN Helle: The crystal structures and magnetic susceptibilities of MnNb 3 S 6 , FeNb 3 S 6 , CoNb 3 S 6 and NiNb 3 S 6 . In: Journal of Physics and Chemistry of Solids . tape 31 , no. 5 , 1970, p. 1057-1067 , doi : 10.1016 / 0022-3697 (70) 90315-X .
  • AY Barkov, RF Martin, YP Men'shikov, YE Savchenko, Y. Thibault, KVO Laajoki: Edgarite, FeNb 3 S 6 , first natural niobium-rich sulfide from the Khibina alkaline complex, Russian Far North: evidence for chalcophile behavior of Nb in a fenite . In: Contributions to Mineralogy and Petrology . tape 138 , no. 3 , 2000, pp. 229-236 , doi : 10.1007 / s004100050559 .
  • John Leslie Jambor , Jacek Puziewicz, Andrew C. Roberts: New mineral names . In: American Mineralogist . tape 85 , 2000, pp. 1843–1847 ( rruff.info [PDF; 379 kB ; accessed on November 27, 2017]).

Web links

Individual evidence

  1. ↑ a b c d 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.  97 .
  2. ↑ Webmineral - Edgarite (English)
  3. ↑ a b c d Edgarite . 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; 61  kB ; accessed on November 27, 2017]).
  4. ↑ a b Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties . 6th completely revised and supplemented edition. Weise, Munich 2014, ISBN 978-3-921656-80-8 .
  5. ↑ Find location list for Edgarit in the Mineralienatlas and Mindat