Uranocircit
| Uranocircit | |
|---|---|
 |
|
| General and classification | |
| other names |
|
| chemical formula | Ba [UO 2 | PO 4 ] 2 · 10-12H 2 O |
|
Mineral class (and possibly department) |
Phosphates , arsenates and vanadates |
|
System no. to Strunz and to Dana |
8.EB.05 ( 8th edition : VII / E.01) 40.02a.03.01 |
| Similar minerals | Autunite , Sabugalite , Saléeit , Zeunerite , Uranospinite |
| Crystallographic Data | |
| Crystal system | tetragonal |
| Crystal class ; symbol | ditetragonal-dipyramidal; 4 / m 2 / m 2 / m |
| Space group | I 4 / mmm (No. 139) |
| Lattice parameters | a = 7.01 Å ; c = 20.46 Å |
| Formula units | Z = 2 |
| Physical Properties | |
| Mohs hardness | 2 to 2.5 |
| Density (g / cm 3 ) | 3.46 |
| Cleavage | completely [001], clearly [100] |
| Break ; Tenacity | shelly to brittle |
| colour | light to dark yellow green |
| Line color | light yellow |
| transparency | transparent to translucent |
| shine | Pearlescent |
| radioactivity | highly radioactive |
| Crystal optics | |
| Refractive indices |
n α = 1.574 n β = 1.583 n γ = 1.588 |
| Birefringence | δ = 0.014 |
| Optical character | biaxial negative |
| Axis angle | 2V = measured: 70 °; calculated: 72 ° |
| Pleochroism | weak: X = colorless; Y = Z = light canary yellow |
| Other properties | |
| Special features | toxic, strong fluorescence |
Uranocircit is a rarely occurring mineral from the class of " phosphates , arsenates and vanadates ", which belongs to the group of uranium mica . It crystallizes in the tetragonal crystal system with the general chemical composition Ba [UO 2 | PO 4 ] 2 · 10-12H 2 O. Since a redefinition in 1963, the mineral is divided into according to its content of crystal water
- Uranocircit-I - Ba [UO 2 | PO 4 ] 2 · 12H 2 O
- Uranocircit-II - Ba [UO 2 | PO 4 ] 2 · 10H 2 O
The mineral status of Uranocircit II was inherited due to its first description before the IMA was founded in 1959 and the new definition of Uranocircit I was initially adopted by the IMA commission CNMNC without further examination, but is no longer recognized.
Uranocircit mainly develops tabular crystals in leafy, stack - shaped mineral aggregates , but is also found in the form of earthy to powdery coatings of light to dark yellow-green in color with light yellow streak color . Contaminated crystals can also take on a correspondingly darker to black color. Uranocircit often looks confusingly similar to the Autunit , but is significantly greener (according to Klockmann, "Zeisiggrün").
Etymology and history
Uranocircit was first discovered near the town of Falkenstein in Vogtland in Saxony. The mineral was first described and named in 1877 by Albin Weisbach (1833–1901). Weisbach himself gave no explanation for his designation. However, the name can be derived from the Latin word circos or the Greek word kirkos ( κίρκος ) for falcon or hawk, based on its uranium content and its type locality .
The type mineral was included by Weißbach in the mineralogical collection of the TU Bergakademie Freiberg in 1874 .
In the records of Paul Heinrich von Groth in 1878, uranocircite is also referred to as barium uranium .
classification
In the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the Uranocircit belonged to the mineral class of "Phosphates, Arsenate and Vanadates" and there to the department of "Uranylphosphate and Uranylvanadate", where it was used together with Autunit , Fritzscheit , Heinrichit , Kahlerit , Metanatroautunit , Nováčekit , Sabugalit , Saléeit , Torbernit , Trögerit , Uranospinit and Zeunerit the "Autunit Group" with the system no. VII / E.01 .
The 9th edition of Strunz's mineral systematics , valid since 2001 and used by the International Mineralogical Association (IMA), assigns the minerals Uranocircit-I and Uranocircit-II also to the class of "Phosphates, Arsenate and Vanadates" and there in the department of "Uranyl phosphates and arsenates". However, this section is further subdivided according to the ratio of uranium oxide complex (UO 2 ) to phosphate, arsenate or vanadate complex (RO 4 ), so that the mineral according to its composition is in the sub-section "UO 2 : RO 4 = 1: 1" is to be found, where together with Autunit, Heinrichit, Kahlerit, Kirchheimerit , Nováčekit-I , Nováčekit-II , Saléeit, Torbernit, Uranospinit, Xiangjiangit and Zeunerit the "Autunitgruppe" with the system no. 8.EB.05 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Uranocircit to the class of "phosphates, arsenates and vanadates", but there in the category of "water-containing phosphates etc.". Here it is together with Metauranocircit in the unnamed group 40.02a.03 within the subdivision of “ Water-containing phosphates etc., with A 2+ (B 2+ ) 2 (XO 4 ) • x (H 2 O), with (UO 2 ) 2+ ”.
Crystal structure
Uranocircite crystallizes tetragonally in the space group I 4 / mmm (space group no. 139) with the lattice parameters a = 7.01 Å and c = 20.46 Å as well as 2 formula units per unit cell .
Uranocircit is made up of phosphate tetrahedra linked with distorted octahedral uranium oxide groups. The phosphate and uranium groups lie in layers that are only weakly held together by water molecules. This gives the typical platy structure, the perfect split direction and the relative softness. When exposed to air, the uranocircite loses part of its crystal water and becomes metauranocircite. The crystals become cloudy and the pieces even more brittle.
properties
The mineral is poisonous due to its barium content and highly radioactive due to its uranium content of up to 43.9% with a specific activity of around 78,650 Bq / g (for comparison: natural potassium 31.2 Bq / g).
Uranocircit shows a bright, green fluorescence under short and long wave UV light . Some Uranocircites fluoresce under blue light.
After some time in the air or through heating, uranocircite loses part of its crystal water and changes to metauranocircite .
Education and Locations
Uranocircite is formed as a secondary mineral in the oxidation zone of uranium deposits, where it is found, among other things, in parallel with autunite and torbernite .
As a rare mineral formation, Uranocircit could only be detected at a few sites, whereby so far (as of 2016) around 90 sites are known. In addition to its type locality Streuberg in Bergen , the mineral occurred in Germany in the nearby mine at Mechelgrün / Zobes ( Neuensalz , see also Zobes / Bergen deposit of the Wismut company ) and at Tirpersdorf in Vogtland and at several locations in the Ore Mountains in Saxony, near Eisenbach and in the Krunkelbach mine near Menzenschwand in Baden-Württemberg as well as on Pauliberg and near Schwandorf in Bavaria.
Damětice in Okres Klatovy in the Czech Republic, where tabular crystals up to one centimeter in diameter were found, are worth mentioning due to the extraordinary finds of uranocircite .
In Austria, the mineral has so far only been found on the Prinzenkogel near Rettenegg in the Fischbacher Alps in Styria.
Other sites are in Australia, Brazil, Bulgaria, China, Democratic Republic of the Congo, France, Japan, Madagascar, Niger, Poland, Portugal, South Korea and the United States of America (USA).
use
Uranocircite is a sought-after mineral sample among collectors due to its beautiful crystal formations and strong fluorescence.
Precautions
Since Uranocircit is a relatively strong alpha-emitting material, the mineral should not get into the organism. Because the crystals break easily into small particles, which then stick to the fingers, hands should be washed immediately after touching and examining the stones to prevent them from being absorbed into the body, where it remains for a very long time and is constant Alpha decay is carcinogenic . After handling the material, the workstation should be examined with a UV lamp - a banknote tester is sufficient - for particles that are conspicuously glowing under UV light, which would otherwise lead to an undetected hazard.
See also
literature
- Albin Weisbach: Mineralogical messages. I. Walpurgin, II. Zeunerite and Uranospinite, III. Uranocircite, IV. Bismuthosphere, V. Roselith, VI. Cobalt spath. In: Yearbook for mining and metallurgy in the Kingdom of Saxony. Abhandlungen, 1877, pp. 42–53 ( PDF 1.6 MB; p. 7 )
- Paul Ramdohr , Hugo Strunz : Klockmann's textbook of mineralogy . 16th edition. Ferdinand Enke Verlag, Stuttgart 1978, ISBN 3-432-82986-8 , p. 655 .
Web links
- Mineral Atlas: Uranocircit (Wiki)
- Thomas Witzke (Stollen Troll): The discovery of Uranocircit
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. 524 .
- ↑ a b c Webmineral - Uranocircite (English)
- ↑ a b c d e f g Uranocircite at mindat.org (English)
- ↑ a b IMA / CNMNC - List of Mineral Names; 2009 (English, PDF 1.8 MB; p. 293)
- ↑ Thomas Witzke (tunnel troll): The discovery of Uranocircit
- ↑ IMA / CNMNC - List of Mineral Names; November 2015 (English, PDF 1.6 MB; p. 293)
- ^ Paul Ramdohr , Hugo Strunz : Klockmanns textbook of mineralogy . 16th edition. Ferdinand Enke Verlag, Stuttgart 1978, ISBN 3-432-82986-8 , p. 655 .
- ^ Henry George Liddell, Robert Scott: A Greek-English Lexicon - kirkos
- ↑ Type mineral catalog of the Mineralogical-Petrographic Institute of the University of Hamburg (Weblink)
- ↑ Hans Lüschen: The names of the stones. The mineral kingdom in the mirror of language . Ott Verlag, Thun and Munich 1968, p. 338 .
- ^ A b Petr Korbel, Milan Novák: Mineral Encyclopedia . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 190 ( Dörfler Natur ).
- ↑ Hans Jürgen Rösler : Textbook of Mineralogy . 4th revised and expanded edition. German publishing house for basic industry (VEB), Leipzig 1987, ISBN 3-342-00288-3 , p. 650 .
- ↑ Mindat - Number of localities for Uranocircit
- ↑ Find location list for Uranocircit at the Mineralienatlas and at Mindat
- ↑ Mineral Atlas: Uranocircit