Barnesite
| Barnesite | |
|---|---|
 |
|
| General and classification | |
| chemical formula | Na 2 [V 5+ 6 O 6 ] • 3H 2 O |
|
Mineral class (and possibly department) |
Oxides and hydroxides |
|
System no. to Strunz and to Dana |
4.HG.45 ( 8th edition : IV / G.12) 47.03.01.03 |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic; 2 / m |
| Room group (no.) | P 2 / m (No. 10) |
| Lattice parameters |
a = 12.17 Å ; b = 3.60 Å; c = 7.78 Å β = 95.0 ° |
| Formula units | Z = 1 |
| Physical Properties | |
| Mohs hardness | 3 |
| Density (g / cm 3 ) | measured: 3.09 to 3.15; calculated: 3.23 |
| Cleavage | completely after {001}, clearly after {100}, {010} |
| colour | strong dark red to brownish red |
| Line color | brownish red |
| transparency | translucent |
| shine | Diamond luster |
| Crystal optics | |
| Refractive indices |
n α = 1.797 to 1.800 n β = 2.010 to 2.040 n γ = 2.040 to 2.080 |
| Birefringence | δ = 0.243 to 0.280 |
| Optical character | biaxial negative |
| Axis angle | 2V = 60 ° (measured) |
| Pleochroism | strong: X = yellow, Y = yellow-orange, Z = red |
| Other properties | |
| Chemical behavior | slowly soluble in dilute hydrochloric acid (HCl) |
Barnesite is a rarely occurring mineral from the mineral class of "oxides and hydroxides". It crystallizes in the monoclinic crystal system with the chemical composition Na 2 [V 5+ 6 O 6 ] · 3H 2 O, and is thus chemically seen a hydrous sodium - Vanadium - oxide .
Barnesite only develops microscopic, needle-like crystals up to about 0.5 millimeters in length and is usually found in the form of fibrous or leafy aggregates and crusty coatings of very shiny, dark red to brownish-red color with a brownish-red streak color .
Etymology and history
Barnesite was first discovered in the “Cactus Rat Mine” at Cisco in the US state of Utah and described in 1963 by Alice D. Weeks, Daphne R. Ross and Richard F. Marvin, after the Canadian physicist and crystallographer William Howard Barnes (1903–1980 ) named.
classification
In the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the barnesite belonged to the mineral class of "oxides and hydroxides" and there to the department of "vanadium oxides (polyvanadates with V 4 + / 5 + )", where it together with Grantsite , Hendersonite , hewettite and metahewettite formed the unnamed group IV / G.12 .
The 9th edition of Strunz's mineral systematics, which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also classifies barnesite in the "V [5,6] Vanadate" division. This is, however, further subdivided according to the crystal structure , whereby the mineral was assigned to the subdivision of "Unclassified Vanadium [V] oxides", where it is the only member of the unnamed group 4.HG.45 .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns barnesite to the class of "phosphates, arsenates and vanadates" and there to the category of "vanadium oxy salts". Here he is together with Grantsit, Hendersonit, Hewettit and Metahewettit in the "Hewettitgruppe" with the system no. 47.03.01 to be found in the sub-section " Vanadium oxy salts (containing water) ".
Education and Locations
Barnesite forms secondarily as a conversion product from other vanadium minerals in small cavities or crack fillings in the oxidation zone of deposits containing vanadium and uranium , but can also arise in weathered black slate . In addition to hewittite and metahewettite, alunite , barite , bokite , gypsum , jarosite and thenardite can also occur as accompanying minerals , depending on the location .
As a rare mineral formation, barnesite could only be detected at a few sites, with around 15 sites being known to date. In addition to its type locality "Cactus Rat Mine", the mineral also emerged in Utah in the "Vanadium Queen Mine" in San Juan County (Utah) . Furthermore, barnesite was found in several ore mines in Montrose County and Mesa County in Colorado, in the "Gibellini Mine" in Eureka County of Nevada and in the Grants District in the counties of Cibola and McKinley in New Mexico.
Other known sites are the Liebenbergite slag dump near Agios Konstantinos in the Greek municipality of Lavrio , the Molinello mine in the Graveglia Valley in the Italian province of Genoa and the vanadium deposits Kurumsak and Balasauskandyk in the Karatau Mountains in southern Kazakhstan.
Crystal structure
Barnesite crystallizes monoclinically in the space group P 2 / m (space group no. 10) with the lattice parameters a = 12.17 Å ; b = 3.60 Å; c = 7.78 Å and β = 95.0 ° and one formula unit per unit cell .
See also
literature
- Alice D. Weeks, Daphne R. Ross, Richard F. Marvin: The occurrence and properties of barnesite, Na 2 V 6 O 16 · 3H 2 O, a new hydrated sodium vanadate mineral from Utah. In: American Mineralogist. Volume 48 (1963), pp. 1187–1195 ( PDF 558.5 kB )
- HT Evans, Jr., JM Hughes: Crystal chemistry of the natural vanadium bronzes. In: American Mineralogist. Volume 75 (1990), pp. 508-521 ( PDF 1.18 MB )
Web links
- Mineral Atlas: Barnesite (Wiki)
- Database-of-Raman-spectroscopy - Barnesite
- American-Mineralogist-Crystal-Structure-Database - Barnesite
Individual evidence
- ↑ a b c d e Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 259 .
- ↑ Webmineral - Barnesite
- ↑ a b Barnesite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF kB )
- ↑ a b c d Mindat - Barnesite
- ↑ Mindat - Number of localities for barnesite
- ↑ Find location list for barnesite in the Mineralienatlas and Mindat