Brunogeierite

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Brunogeierite
General and classification
other names
  • Germanium ferrite spinel
  • IMA 1972-004
chemical formula
  • Fe 2+ 2 Ge 4+ O 4
  • Fe 2 (Ge, Fe) O 4
  • (Ge x Fe 1-x ) Fe 2 O 4
Mineral class
(and possibly department) 		Silicates and germanates (formerly oxides and hydroxides)
System no. to Strunz
and to Dana 		9.AC.15 ( 8th edition : IV / B.04)
02/07/02/07
Crystallographic Data
Crystal system cubic
Crystal class ; symbol cubic hexakisoctahedral; 4 / m  3  2 / m
Space group Fd 3 m (No. 227)Template: room group / 227
Lattice parameters a  = 8.41  Å
Formula units Z  = 8
Physical Properties
Mohs hardness 4.5 to 5
Density (g / cm 3 ) calculated: 5.51
Cleavage is missing
colour gray to gray-black with brownish, internal reflections in incident light
Line color not defined
transparency opaque (opaque)
shine weak metallic luster
magnetism ferromagnetic

Brunogeierite is a very rarely occurring mineral from the mineral class of "silicates and germanates" (formerly oxides and hydroxides, see classification ) with the idealized chemical composition Fe 2+ 2 Ge 4+ O 4 and is therefore chemically an iron - germanium - oxide . Structurally, however, brunogeierite belongs to the group of spinels and was therefore also referred to as germanium ferrite spinel by its first description . According to the general notation for spinels (AB 2 X 4 ), the formula for brunogeierite can be given as GeFe 2+ 2 O 4 .

Brunogeierite crystallizes in the cubic crystal system , but only very rarely develops crystals up to about 5 mm in size that are visible to the naked eye . It is usually found, surrounded by stottite , in the form of crusty coatings of 40 to 50 μm on tennantite , which in turn contains inclusions of renierite . Brunogeierite can also be included by sphalerite and magnetite .

The mineral is generally opaque and gray to gray-black in color with brownish internal reflections in the incident light microscope . The surfaces of the crystals have a weak metallic luster .

Etymology and history

Brunogeierite was discovered for the first time in the world-famous Cu-Pb-Zn-Ag-Ge-Cd deposit "Tsumeb Mine" (also Tsumcorp Mine ) near the mining town of the same name in the Oshikoto region of Namibia . It was first described in 1972 by Joachim Ottemann and Bernhard Nuber , who named the mineral after the former chief mineralogist of Tsumcorp Bruno H. Geier (1902–1987) in order to honor his services to research into the mineral paragenesis of Tsumeb.

A storage location for the Brunogeierit type material has not been defined.

classification

The current classification of the International Mineralogical Association (IMA) is one of the Brunogeierit to spinel supergroup , where he together with Ahrensit , Filipstadit , Qandilit , ringwoodite and Ulvöspinell forms the Ulvöspinell subgroup within the Oxispinelle.

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , brunogeierite belonged to the mineral class of "oxides and hydroxides" and there to the department of "oxides with a metal: oxygen ratio = 3: 4 (spinel type M 3 O 4 and related compounds) ", where together with coulsonite , magnesiocoulsonite , qandilite, ulvöspinell and vuorelainenite, the group of" V / Ti / Ge spinels "with the system no. IV / B.04 .

The 9th edition of Strunz's mineral systematics, which has been in effect since 2001 and is used by the IMA, initially also classified brunogeierite in the oxides division with a substance ratio of “metal: oxygen = 3: 4 and comparable”. This is further divided according to the relative size of the participating cations , so that the mineral was found according to its composition in the subsection "With only medium-sized cations" where it along with chromite , Cochromit , Coulsonit, Cuprospinell , Filipstadit, Franklinite , Gahnit , Galaxit , Hercynite , jacobsite , magnesiochromite , magnesiocoulsonite, magnesioferrite , magnetite , manganochromite , nichromite (N), qandilite, spinel , trevorite , ulvöspinell, vuorelainenite and zincochromite the "spinel group" with the system no. 4.BB.05 formed.

Since 2011, however, brunogeierite has been classified in the class of "silicates and germanates" and is there together with ringwoodite in the newly defined "ringwoodite group" with the system no. 9.AC.15 in the subsection of “ Island silicates without further anions ; To find cations in octahedral [6] coordination ”.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns brunogeierite, like the outdated systematics according to Strunz, to the class of "oxides and hydroxides" and there in the section "multiple oxides", where it together with magnesioferrite, jacobsite, magnetite , Franklinite, Trevorite and Cuprospinell in the " iron subgroup " with the system no. 07.02.02 can be found in the subsection "Multiple Oxides (A + B 2+ ) 2 X 4 , Spinel Group ".

Chemism

The idealized, theoretical compound Fe 2+ 2 Ge 4+ O 4 consists of 44.98% iron (Fe), 29.25% germanium (Ge) and 25.77% oxygen (O). However, the electron beam microanalysis of the type material from Tsumeb showed that a small part of the germanium (0.05 to 0.13% ) is replaced ( substituted ) by iron . The correspondingly adapted empirical formula is (Ge x Fe 1-x ) Fe 2 O 4 with a value for x = 0.87 to 0.95.

Crystal structure

Brunogeierite crystallizes cubically in the space group Fd 3 m (space group no. 227) with the lattice parameters a  = 8.41  Å and 8 formula units per unit cell . Template: room group / 227

Education and Locations

At its type locality, the "Tsumeb Mine" in Namibia, brunogeierite formed in the polymetallic ore body of the lower oxidation zone at a depth of about 930 meters, more precisely below the 29th level, which is at a depth of 922.6 m. Galena , tennantite , renierite , smithsonite and stottite as well as subordinate cerussite occurred here as accompanying minerals .

Brunogeierite is one of the very rare mineral formations and has therefore only been known in a few samples from two countries. In addition to the "Tsumeb Mine", which is the only place where it was found in Namibia so far, the mineral also appeared in some places in France, more precisely in the Occitania region .

In a lead-zinc deposit near Carboire in the Ariège department , besides brunogeierite, the mineral carboirite , which was first discovered there , the likewise rare germanium minerals argutite and briartite and, as another spinel, magnetite can be found . Brunogeierite was also found in the nearby villages of Saubé (municipality of Cauflens) and Sentein-Bentaillou (municipality of Saint-Girons ).
In the Haute-Garonne department , brunogeierite was found together with argutite, cassiterite and sphalerite in the Plan d'Argut and Rimbatz deposits near Argut-Dessous , at several sites in the municipality of Bagnères-de-Luchon as well as at Pal Bidao and Pale de Raze (municipality of Saint -Béat ) found.
In the Hautes-Pyrénées department , brunogeierite also appeared together with argutite, cassiterite and sphalerite near Lèches near the city of Lourdes .

Brunogeierite can also be produced synthetically by mixing iron (Fe), magnetite (Fe 3 O 4 ) and germanium (IV) oxide (GeO 2 ) in a ratio of 1: 1: 2 and heating at 1000 ° C for six days, resulting in well-developed octahedral crystals.


See also

literature

Monographs
  • Joachim Ottemann, Bernhard Nuber: Brunogeierit, a germanium ferrite spinel from Tsumeb . In: New yearbook for mineralogy, monthly books . 1972, p. 263-267 .
  • Michael Fleischer : New mineral names . In: American Mineralogist . tape 58 , 1973, p. 347–349 (English, rruff.info [PDF; 354 kB ; accessed on September 9, 2018]).
  • Mark David Welch, MA Cooper, Frank C. Hawthorne: The crystal structure of brunogeierite, Fe 2 GeO 4 spinel . In: Mineralogical Magazine . tape 65 , no. 3 , 2001, p. 441–444 (English, rruff.info [PDF; 76 kB ; accessed on September 9, 2018]).
  • Jan Cempírek, Lee A. Groat: Note on the formula of brunogeierite and the first bond-valence parameters for Ge 2+ . In: Journal of Geosciences . tape 58 , 2013, p. 71–74 , doi : 10.3190 / jgeosci.130 (English, cuni.cz [PDF; 462 kB ; accessed on September 9, 2018]).
Compendia

Web links

Individual evidence

  1. ↑ a b c IMA / CNMNC List of Mineral Names; March 2018 (English; PDF 1.65 MB)
  2. ^ 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.  189 (English).
  3. ^ A b Michael Fleischer : New mineral names . In: American Mineralogist . tape  58 , 1973, p. 347–349 (English, rruff.info [PDF; 354 kB ; accessed on September 9, 2018]).
  4. ↑ Webmineral - Brunogeierite (English)
  5. ↑ 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 .
  6. ↑ a b c d e Brunogeierite . 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; 67  kB ; accessed on September 9, 2018]).
  7. ↑ a b Friedrich Klockmann : Klockmanns textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp.  507 (first edition: 1891).
  8. ↑ a b c d Joachim Ottemann, Bernhard Nuber: Brunogeierit, a germanium ferrite spinel from Tsumeb . In: New yearbook for mineralogy, monthly books . 1972, p. 263-267 .
  9. ↑ Mineralienatlas : Type locality Tsumeb Mine, Oshikoto, Namibia
  10. ↑ Cristian Biagioni, Marco Pasero: The systematics of the spinel-type minerals: An overview . In: American Mineralogist . tape 99 , no. 7 , 2014, p. 1254–1264 , doi : 10.2138 / am.2014.4816 (English, preliminary version online [PDF]).
  11. ↑ PA Williams, F. Hatert, M. Pasero, SJ Mills: IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) - Newsletter 9 . In: Mineralogical Magazine . tape 75 , no. 4 , August 2011, p. 2535–2540 (English, rruff.info [PDF; 123 kB ; accessed on September 10, 2018]).
  12. ^ Mineralienatlas: Brunogeierite
  13. ↑ Find location list for brunogeierite at the Mineralienatlas and at Mindat