Daubréeit
| Daubréeit | |
|---|---|
| General and classification | |
| chemical formula |
|
|
Mineral class (and possibly department) |
Halides - oxyhalides |
|
System no. to Strunz and to Dana |
3.DC.25 ( 8th edition : III / D.09) 02/10/01/03 |
| Crystallographic Data | |
| Crystal system | tetragonal |
| Crystal class ; symbol | ditetragonal-dipyramidal; 4 / m 2 / m 2 / m |
| Space group | P 4 / nmm (No. 129) |
| Lattice parameters | a = 3.86 Å ; c = 7.41 Å |
| Physical Properties | |
| Mohs hardness | 2 to 2.5 |
| Density (g / cm 3 ) | measured: 6.4 to 6.5; calculated: [7.70] |
| Cleavage | completely after {001} |
| colour | creamy white, pale yellow, yellow-brown |
| Line color | White |
| transparency | transparent to opaque |
| shine | Greasy sheen, silk sheen |
| Crystal optics | |
| Refractive indices |
n ω = 2.150 n ε = 1.910 |
| Birefringence | δ = 0.240 |
| Optical character | uniaxial negative |
Daubréeit is a very rarely occurring mineral from the mineral class of " halides ". It crystallizes in the tetragonal crystal system with the idealized chemical composition BiO (OH). Since in naturally occurring daubréeit, however, part of the hydroxide is usually replaced ( substituted ) by chlorine , the formula is also given in many sources as BiO (OH, Cl). The hydroxide ions or the element chlorine indicated in the round brackets can represent each other in the formula ( substitution , diadochy), but are always in the same proportion to the other components of the mineral.
Daubréeit has so far only been found in the form of opaque, massive to columnar mineral aggregates with a creamy white or pale yellow to yellow-brown color and a fat to silk-like sheen . As a thin section under the transmitted light microscope, however, it appears colorless and transparent. With a Mohs hardness of 2 to 2.5, Daubréeit is one of the soft minerals that can be scratched with a fingernail and is also easily malleable. Similar to graphite , curved chips can be scraped off with a knife .
Daubréeit is in pure form the hydroxide analog of the closely related Bismoclit (BiOCl).
Etymology and history
Daubréeit was first discovered on Cerro Tazna (Cerro Tasna) in the Atocha-Quechisla district in the Bolivian province of Nor Chichas and described in 1876 by Ignacy Domeyko , who named the mineral after the French geologist Gabriel Auguste Daubrée (1814-1896).
Type material of the mineral is found in the Muséum national d'histoire naturelle in Paris (France) (Catalog No. 94.247) and in the collections of the Geoscientific Center of the University of Göttingen (Catalog No. GZG.MIN.3.3.63.1 / UG023-025) kept. The latter received the type material indirectly via the mineral collection bequeathed to the university by Friedrich Wöhler in 1877, which also contained a sample of the Daubréeits as a gift from Ignacy Domeyko.
classification
Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the Daubréeit belonged to the mineral class of the "halides" and there to the department of the "oxyhalides", where together with bismoclite , matlockite , rorisit , zavaritskit and zhangpeishanite it belongs to the "matlockite group “With the system no. III / D.09 formed.
The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), classifies the Daubréeit in the expanded section of "Oxyhalides, hydroxyhalides and related double halides". This is further subdivided according to the predominant metals in the compound, so that the mineral can be found according to its composition in the sub-section "With Pb (As, Sb, Bi) without Cu", where it is also found together with bismoclite, matlockite, rorisite, Zavaritskit and Zhangpeishanit the "Matlockitgruppe" with the system no. 3.DC.25 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Daubréeit to the class of "halides" and there in the department of "@@@". Here it can be found together with Bismoclit and Zavaritskit in the unnamed group 10.02.01 within the subsection “ Oxyhalides and hydroxyhalides with the formula A (O, OH) X q ”.
Crystal structure
Daubréeit crystallizes tetragonally in the space group P 4 / nmm (space group no. 129) with the lattice parameters a = 3.86 Å and c = 7.41 Å as well as two formula units per unit cell .
Education and Locations
Daubréeit is secondary to the weathering of bismuth or the conversion of bismuthinite (Bi 2 S 3 ) and is mostly found in a mixture with various clay minerals (including kaolinite ) in the oxidation zone of bismuth deposits .
Daubréeit is one of the very rare mineral formations, of which only a few samples exist that have been collected at less than 10 known sites so far (as of 2015). Apart from its type locality Cerro Tazna, more precisely in the ore mine of the same name there, the mineral only appeared in Bolivia in the Chorolque Mine at the nearby Cerro Chorolque within the mountainous region of Cordillera de Chichas (Potosí).
Other previously known sites are the Rio Mine (Rio Marina Mine) in the municipality of Rio on the Italian island of Elba and the Outlaw Mine in the Round Mountain district in Nye County of Nevada, a soap deposit on Josephine Creek in the county of Oregon of the same name and two pits ( Eagle and Blue Bell) near Eureka and Tintic, respectively, in Juab County of Utah in the United States of America .
See also
literature
- I. Domeyko: Daubréite (oychlorure de bismuth), espèce de minérale nouvelle. In: Comptes rendus hebdomodaires des séances de l'Académie des Sciences Volume 82 (1876), pp. 922-923
- Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke , Stuttgart 1978, ISBN 3-432-82986-8 , pp. 495 (first edition: 1891).
Web links
- Mineral Atlas: Daubréeit (Wiki)
Individual evidence
- ↑ a b c IMA / CNMNC List of Mineral Names; March 2015 (PDF 1.5 MB)
- ↑ 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. 177 .
- ↑ a b c d Daubréeite . 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; 58 kB ]).
- ↑ 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 .
- ↑ a b c d e Mindat - Daubréeite
- ↑ Webmineral - Daubréeite
- ↑ Faculty of Geosciences and Geography of the University of Göttingen - Type Material Mineralogy ( Memento from May 31, 2015 in the web archive archive.today )
- ↑ List of localities for Daubréeit at the Mineralienatlas and at Mindat