Tyuyamunit
| Tyuyamunit | |
|---|---|
 |
|
| General and classification | |
| chemical formula | Ca [UO 2 | VO 4 ] 2 · 6-8H 2 O |
|
Mineral class (and possibly department) |
Oxides and hydroxides |
|
System no. to Strunz and to Dana |
4.HB.25 ( 8th edition : VII / E.11) 40.02a.26.01 |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-dipyramidal; 2 m 2 m 2 m |
| Room group (no.) | Pnan (No. 52) |
| Lattice parameters | a = 10.63 Å ; b = 8.36 Å; c = 16.96 Å |
| Formula units | Z = 4 |
| Physical Properties | |
| Mohs hardness | 1.5 to 2 |
| Density (g / cm 3 ) | 3.57 to 4.35 |
| Cleavage | perfect according to {001}, good according to {010} and {100} |
| Break ; Tenacity | uneven |
| colour | yellow, green-yellow |
| Line color | light yellow |
| transparency | translucent, opaque |
| shine | Silk gloss, wax gloss, matt |
| radioactivity | very strong |
| Crystal optics | |
| Refractive indices |
n α = 1.675 n β = 1.860 to 1.870 n γ = 1.885 to 1.895 |
| Birefringence | δ = 0.210 to 0.220 |
| Optical character | biaxial negative |
| Axis angle | 2V = measured: 30 to 45 °; calculated: 34 ° |
| Pleochroism | weak: X = almost colorless, Y = weak canary yellow, Z = canary yellow |
| Other properties | |
| Special features | light green fluorescence under short-wave UV light |
Tyuyamunit is a rather seldom occurring uranium - vanadium mineral from the mineral class of " oxides and hydroxides ". It crystallizes in the orthorhombic crystal system with the chemical composition Ca [UO 2 | VO 4 ] 2 · 6–8H 2 O and develops mostly massive mineral aggregates , but rarely also tabular, sometimes fan-shaped crystals of yellow to greenish-yellow color.
Etymology and history
Tyuyamunit was first described by Konstantin Nenadkewitsch in 1912 and named after the type locality, the Tyuya-Muyun mine in Kyrgyzstan .
The type mineral is located at the Russian Academy of Sciences in the Mineralogical Museum " Alexander Fersman " in Moscow , Russia .
classification
In the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the Tyuyamunit belonged to the mineral class of " phosphates , arsenates and vanadates " and there to the department of "uranyl phosphates / arsenates and uranyl vanadates ", where it belonged together with carnotite , curienite , Francevillit , Margaritasite , metatyuyamunit , metavanuralite , sengierite , strelkinite and vanuralite the group of "uranyl group vanadates with [UO 2 ] 2+ - [V 2 O 8 ] 6− " with the system no. VII / E.11 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), assigns the Tyuyamunit to the class of "oxides and hydroxides" and there in the division of "V [5,6] Vanadates" . This is further subdivided according to the crystal structure, so that the mineral can be found in the sub-section "Uranyl group vanadate (Sorovanadate)" according to its structure, where it is only group 4 together with its dehydrated meta form, the metatyuyamunite . HB.25 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Tyuyamunit to the class of "phosphates, arsenates and vanadates", like the outdated Strunz'sche systematics, but there it belongs to the department of "water-containing phosphates etc." Here it is together with the metatyuyamunit in the unnamed group 40.02a.26 within the subdivision of “Water-containing phosphates etc., with A 2+ (B 2+ ) 2 (XO 4 ) × x (H 2 O), with (UO 2 ) 2+ ”to be found.
Crystal structure
Tyuyamunit crystallizes orthorhombically in the space group Pnan (space group no. 52) with the lattice parameters a = 10.63 Å ; b = 8.36 Å and c = 16.96 Å as well as 4 formula units per unit cell . However, the values given here are used by Stern et al. described as belonging to the Metatyuyamunit.
properties
The mineral is highly radioactive due to its uranium content of up to 51.8% . Taking into account the proportions of radioactive elements in the idealized empirical formula and the subsequent decays of the natural decay series, a specific activity of about 92.8 k Bq / g is specified for the mineral (for comparison: natural potassium 0.0312 kBq / g). The quoted value can vary significantly depending on the mineral content and the composition of the levels; selective enrichment or depletion of the radioactive decay products is also possible and changes the activity.
The water content of Tyuyamunit is zeolitic in nature, which means that the water of crystallization can fluctuate depending on the surrounding humidity . In a dry environment, Tyuyamunit dehydrates to Metatyuyamunit with the formula Ca [(UO 2 ) 2 (VO 4 ) 2 ] · 3-5H 2 O.
Tyuyamunit is visually difficult to distinguish from other uranyl vanadates such as carnotite . It shows a light green fluorescence under short-wave UV light.
Modifications and varieties
In a dry environment, Tyuyamunite dehydrates while releasing part of its crystal water to Metatyuyamunite Ca [UO 2 | VO 4 ] 2 · 3–5H 2 O. Metatyuyamunite crystallizes orthorhombically in the space group Pnam with the lattice parameters a = 10.54 Å; b = 8.49 Å and c = 17.34 Å and 4 formula units per unit cell. Other authors report the following unit cell for Metatyuyamunit, found in Romania: orthorhombic, with the lattice parameters a = 10.77 Å; b = 8.53 Å and c = 17.62 Å and 4 formula units per unit cell.
Education and Locations
Tyuyamunit forms in the oxidation zone of uranium-vanadium deposits on sandstone matrix . It occurs in paragenesis with, among others, autunite , carnotite , corvusite , gypsum , malachite , metatyuyamunite , vesignietite and volborthite . Finds of Tyuyamunite or Metatyuyamunite in caves suggest that this mineral is formed from hydrothermal solutions.
So far, Tyuyamunit has been found at several sites around the world. The most important sites are above all those of the Colorado Plateau in Utah and Arizona in the United States .
Precautions
Due to the toxicity and the strong radioactivity of the mineral, mineral samples from the Tyuyamunit should only be kept in dust- and radiation-proof containers, but especially never in living rooms, bedrooms or work rooms. Absorption into the body (incorporation, ingestion ) should also be prevented in any case and, for safety, direct body contact should be avoided and respiratory protection mask and gloves should be worn when handling the mineral .
See also
literature
- Tyuyamunite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 65.3 kB )
- Metatyuyamunite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 64.5 kB )
- Petr Korbel, Milan Novák: Encyclopedia of Minerals . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 191 .
Web links
- Mineral Atlas: Tyuyamunit (Wiki)
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. 255 .
- ↑ a b Webmineral - Tyuyamunite (English)
- ↑ a b c d e Mindat - Tyuyamunite (English)
- ↑ KA Nenadkewitsch: Тюямунитъ - новый минеральный видъ ( Tyuyamunite - a new mineral species ), In: Bulletin de l'Académie Impériale des Sciences de St.-Pétersbourg , Volume 6 (1912) , Russian , pp. 945–946 ( PDF . 945–946) )
- ↑ a b c TW Stern, LR Stieff, MN Girhard, R. Meyrowitz: The Occurrence and Properties of Meta-Tyuyamunit Ca [(UO 2 ) 2 (VO 4 ) 2 ] · 3–5H 2 O , In: American Mineralogist , Volume 41 (1956), pp. 187-201 ( PDF 894 kB )
- ↑ a b c BP Onac, J. Kearns, P. Damm, WB White, S. Matyasi: "Hydrothermal Genesis of Metatyuyamunite, Ca (UO2) 2 (VO4) 2 • 3-5H2O in the Valea Rea Cave, Romania" Conference contribution in: "13th International Congress of Speleology, 4th Speleological Congress of Latin América and Caribbean, 26th Brazilian Congress of Speleology" Brasília DF, 15-22 de julho de 2001 ( PDF, English, online )