Uranospathite
| Uranospathite | |
|---|---|
 |
|
| General and classification | |
| chemical formula |
|
|
Mineral class (and possibly department) |
Phosphates, arsenates, vanadates |
|
System no. to Strunz and to Dana |
8.EB.25 ( 8th edition : VII / E.04) 40.02a.22.01 |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-pyramidal; mm2 |
| Room group (no.) | Pnn2 (No. 34) |
| Lattice parameters | a = 30.020 Å ; b = 7.0084 Å; c = 7.0492 Å |
| Formula units | Z = 2 |
| Physical Properties | |
| Mohs hardness | 2.5 |
| Density (g / cm 3 ) | 2.5 |
| Cleavage | perfect after {001}, good after {100}, indistinct after {010} |
| colour | yellow, light green |
| Line color | yellow white |
| transparency | translucent |
| shine | Please complete |
| radioactivity | highly radioactive |
| Crystal optics | |
| Refractive indices |
n α = 1.492 n β = 1.510 n γ = 1.521 |
| Birefringence | δ = 0.029 |
| Optical character | biaxial negative |
| Axis angle | 2V = 69 ° (measured); 70 ° (calculated) |
| Pleochroism | X = pale yellow, Y = Z = deep yellow |
| Other properties | |
| Special features | dehydrated to sabugalite ; yellow-green fluorescence under long-wave UV light |
Uranospathite is a rarely occurring mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the orthorhombic crystal system with the chemical composition
Al 1 – x □ x [(UO 2 ) (PO 4 )] 2 (H 2 O) 20 + 3x F 1–3x , 0 <x <0.33 (also simplified (Al, ☐) (UO 2 ) 2 F (PO 4 ) 2 · 20H 2 O) and is chemically a hydrous aluminum - uranyl - phosphate .
Uranospathite often develops latte-like, pale green to yellow crystals .
Etymology and history
Uranospathite was first described by Hallimond in 1915. The mineral was named after its uranium content and the Greek word "σπάθη" (spathe), which means something like "sword" or "blade", to indicate the crystal habit.
The type mineral is located at the Natural History Museum in London.
classification
Already in the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the uranospathite belonged to the mineral class of "phosphates, arsenates, vanadates" and there to the department of "uranyl phosphates and uranyl vanadates", where together with arsenuranospathite it belongs to the unnamed group VII / E.04 made.
The 9th edition of Strunz's mineral systematics, which has been in force since 2001 and is used by the International Mineralogical Association (IMA), also assigns uranospathite to the class of "phosphates, arsenates and vanadates" and there in the department of "uranyl phosphates and arsenates". However, this section is further subdivided according to the molar ratio of uranium oxide complex (UO 2 ) and phosphate or arsenate complex (RO 4 ), so that the mineral can be found in the sub-section "UO 2 : RO 4 = 1: 1" according to its composition , where together with arsenuranospathite the "uranospathite group" with the system no. 8.EB.25 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the to the class of "phosphates, arsenates, vanadates", but there in the category of "water-containing phosphates etc., with hydroxyl or halogen". Here he is the only member of the unnamed group 40.02a.22 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
Uranospathite crystallizes orthorhombically in the space group Pnn2 with the lattice parameters a = 30.020 Å ; b = 7.008 Å and c = 7.049 Å as well as two formula units per unit cell . The mineral crystallizes in layers of the autunite type. The aluminum ions form isolated octahedral complexes with the water of crystallization , which are located between the uranyl phosphate layers. The uranyl phosphate layers consist of corner-linked phosphate tetrahedra and uranyl octahedra. A complex network of crystalline water molecules holds these layers together through hydrogen bonds . An X-ray analysis of the single crystal structure of uranospathite showed an occupancy ratio of only 86% for the aluminum ions. Due to this discrepancy, it could be shown by wavelength dispersive X-ray spectroscopy that fluoride ions must also be present in the structure. Due to the small difference in the electron density distribution between fluorine (F) and oxygen (O), these ions could not be localized in the single crystal structure analysis. The authors of the study assume that a very small proportion of the water that is coordinated to the aluminum is partially replaced by fluoride ions, so that the following empirical formula results when applying the principle of electroneutrality : Al 1 – x □ x [ (UO 2 ) (PO 4 )] 2 (H 2 O) 20 + 3x F 1-3x , 0 <x <0.33.
properties
The mineral is radioactive due to its uranium content of up to 42.12% . Taking into account the proportions of the radioactive elements in the idealized empirical formula and the Folgezerfälle of the natural decay chains a specific activity of about 75.4 k for the mineral Bq stated / g (compared to 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.
In a dry environment Uranospathit dehydrated at room temperature to Sabugalit .
Uranospathite shows a yellow-green fluorescence under long-wave UV light .
Education and Locations
Uranospathite forms as a secondary mineral in the oxidation zone of uranium deposits . It performs together with Bassetit , among others .
There are only a few uranospathite sites in the world. In England it is only known from its type locality, the Basset Mines. In Germany, uranospathite is only known from the Krunkelbach mine near Menzenschwand and from the "Weißer Hirsch" mine near Neustädtel . In Switzerland it is known from La Creusaz in the canton of Valais. The other known sites are the Radium Hill Mine in Australia, Xiushui in China, Jáchymov in the Czech Republic, in the Limousin region in France, Montescheno in Italy, Beaufort West in South Africa, in Badajoz and Cáceres in Spain and in the Paradox Valley in the UNITED STATES.
Precautions
Due to the toxicity and the strong radioactivity of the mineral, mineral samples of uranospathite 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
Web links
- Mineral Atlas: Uranospathite (Wiki)
literature
- Kurt Walenta: Uranospathite and arsenuranospathite. In: Mineralogical Magazine , Volume 42, March 1978, pp. 117–128 ( PDF 857 kB , English)
- Uranospathite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 63.9 kB ).
Individual evidence
- ↑ a b c d Andrew J. Locock, William S. Kinman, Peter C. Burns: The structure and composition of uranospathite, Al 1 – x □ x [(UO 2 ) (PO 4 )] 2 (H 2 O) 20 + 3x F 1–3x , 0 <x <0.33, a non-centrosymmetric fluorine-bearing mineral of the autunite group, and of a related synthetic lower hydrate, Al 0.67 □ 0.33 [(UO 2 ) (PO 4 )] 2 ( H 2 O) 15.5 . In: Canadian Mineralogist . 43, 2005, pp. 989-1003 ( PDF (English), 1.2 MB ).
- ↑ a b IMA / CNMNC List of Mineral Names; March 2014 (PDF 1.5 MB)
- ↑ a b c d Webmineral - Uranospathite (English)
- ↑ a b c d e Mindat - Uranospathite (English)
- ↑ Kurt Walenta: Uranospathite and arsenuranospathite. In: Mineralogical Magazine , Volume 42, March 1978, p. 119 ( PDF 857 kB , English)