Uranospinite
| Uranospinite | |
|---|---|
 |
|
| General and classification | |
| other names |
Calcium arsenuranite |
| chemical formula | Ca [UO 2 | AsO 4 ] 2 · 10H 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.02.01 |
| 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 = 7.15 Å ; c = 20.61 Å |
| Formula units | Z = 2 |
| Frequent crystal faces | (001) |
| Physical Properties | |
| Mohs hardness | 2 to 3 |
| Density (g / cm 3 ) | measured: 3.45; calculated: 3.30 |
| Cleavage | completely {001}, clearly {100} |
| Break ; Tenacity | brittle |
| colour | lemon yellow to siskin green |
| Line color | light yellow |
| transparency | translucent |
| shine | Waxy sheen, pearlescent |
| radioactivity | highly radioactive |
| Crystal optics | |
| Refractive indices |
n α = 1.550 n β = 1.567 to 1.582 n γ = 1.572 to 1.587 n ω = 1.572 to 1.587 n ε = 1.550 to 1.560 |
| Birefringence | δ = 0.022 to 0.027 |
| Optical character | uniaxial (abnormally biaxial) negative |
| Axis angle | 2V = 50 ° (calculated) |
| Pleochroism | Visible: O = Y = Z = light yellow E = X = almost colorless |
| Other properties | |
| Chemical behavior | easily dehydrates to metauranospinite |
| Special features | yellow-green luminescence with long-wave UV radiation , toxic |
Uranospinit (also Calciumarsenuranit ) is a very rare occurring mineral from the mineral class of phosphates, arsenates and vanadates with the chemical composition Ca [UO 2 | AsO 4 ] 2 · 10H 2 O, making it chemically seen a hydrous calcium - uranyl - arsenate .
Uranospinite crystallizes in the tetragonal crystal system , but only rarely develops thin tabular crystals up to about one millimeter in size. It is mostly found in the form of crusty coatings and aggregates of intergrown crystals.
The translucent crystals are lemon-yellow or yellow-green to siskin-green in color. The line color , however, is light yellow. The density is 3.45 g / cm³ and the Mohs hardness is between 2 and 3.
Etymology and history
Uranospinite was discovered in 1871 by Albin Weisbach in the “Weißer Hirsch” mine ( Schneeberg ) in Neustädtel in the Ore Mountains ( Saxony , Germany ), which is also the type locality. It was also described and named as an independent mineral two years later by Weisbach.
The name Uranospinit has its origin in the uranium content and from the Greek "spinos" (green finch), which indicates the green color.
Type material , i.e. mineral samples from the type locality, is stored in the Museum of Mineralogy and Geology Dresden and in the Technical University Bergakademie Freiberg in Germany under catalog no. 21722 or 21725 kept.
classification
Already in the outdated, but partly still in use 8th edition of the mineral systematics according to Strunz , the uranospinite belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "uranyl phosphates / arsenates and uranyl vanadates", where together with Autunit , Fritzscheit , Heinrichit , Kahlerit , Nováčekit , Sabugalit , Saléeit , Torbernit , Trögerit , Uranocircit and Zeunerit the "Autunit Group" with the system no. VII / E.01 .
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 classifies uranyl phosphates and arsenates in the category of uranyl phosphates. However, this is further subdivided according to the molar ratio of uranyl (UO 2 ) to the phosphate, arsenate or vanadate complex (RO 4 ), so that the mineral according to its composition in the sub-section “UO 2 : RO 4 = 1: 1 " Can be found where together with Autunit, Heinrichit, Kahlerit, Kirchheimerit , Metarauchit , Nováčekit-I , Nováčekit-II , Saléeit, Torbernit, Uranocircit-I , Uranocircit-II , Xiangjiangit and Zeunerit the" Autunit group "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 uranium spinite to the class of "phosphates, arsenates and vanadates" and there in the category of "water-containing phosphates etc.". Here he is the only member / together with in the unnamed group 40.02a.02 within the subdivision "Water-containing phosphates etc., with A 2+ (B 2+ ) 2 (XO 4 ) × x (H 2 O), with ( UO 2 ) 2+ ”.
Crystal structure
Almost all sources indicate a tetragonal symmetry for uranospinite. According to the mineralogical tables according to Strunz and Nickel, uranospinite crystallizes in the space group I 4 / mmm (space group no. 139) with the lattice parameters a = 7.15 Å and c = 20.61 Å as well as two formula units per unit cell .
The optical biaxiality observed in many crystals with axis angles of 2V = 0–62 ° is, however, an indication that the true symmetry of uranospinite is lower. The mineral database Webmineral.com specifies the space group Pnma (space group no. 62) for uranospinite , which corresponds to the orthorhombic crystal class orthorhombic-dipyramidal; 2 / m 2 / m 2 / m . The lattice parameters are given as a = 14.35 Å, b = 20.66 Å and c = 7.17 Å with 4 formula units per unit cell.
The crystal structure is characterized by uranyl phosphate layers that are parallel to the (001) plane. Arsenic 5+ is tetrahedral surrounded by 4 oxygen atoms, the U 6+ octahedral by 6 oxygen atoms. The AsO 4 tetrahedra are linked with UO 6 octahedra over all 4 corners , the UO 6 octahedra over 4 corners with PO 4 tetrahedra.
The water molecules and the Ca ions are located between the uranyl arsenate layers. Every Ca 2+ is octahedrally coordinated by 6 water molecules. The other 4 water molecules are not directly bound to any cation. However, with a complex system of hydrogen bonds, they contribute to a balanced distribution of the charges and thus to the stabilization of the structure.
properties
morphology
Uranospinite forms square to rectangular, tabular crystals, the shape of which is dominated by the {001} surfaces. Outwardly it can look very similar to the Autunit .
Also, epitaxial , that is, according to certain crystallographic axes oriented, adhesions Zeunerit are known.
physical and chemical properties
Uranospinite fluoresces yellow-green under long-wave UV radiation .
Due to the uranium and arsenic it contains , uranospinite is radioactive , highly toxic and carcinogenic . The former in particular has a very long retention time in the body and is massively damaged by the continuous alpha radiation .
The mineral has a specific activity of around 82 k Bq / g (for comparison: natural potassium 31.2 Bq / g).
As with the structurally related minerals Saléeit , Torbernite and Zeunerite , the water content of uranospinite fluctuates from occurrence to occurrence. Uranospinite easily dehydrates to metauranospinite with 8H 2 O.
Education and Locations
Uranospinite is secondary to the weathering of uranium and arsenic minerals ( uraninite ) in the oxidation zone of hydrothermal and sedimentary uranium deposits.
In the uranium deposit near Schneeberg in Saxony, Uranospinite is associated with Metazeunerite , Metauranocircite , Uranophane , Trögerite , Walpurgite , Uranosphaerite , Asselbornite as well as quartz , Churchite- (Y) , dignified bismuth and goethite .
In the Cherkasar deposit in Uzbekistan , uranospinite occurs together with schoepite , paraschoepite , arsenuranylite , metazeunerite and nováčekite.
Other documented deposits are the Clara mine near Oberwolfach in the Black Forest , the Sophia mine near Wittichen , the Gottesehre mine near Urberg , the Rabéjac uranium deposit near Lodève (Hérault department) in France , in Tyndrum , Perthshire , Scotland , the Talmessi mine near Anarak in Iran , Myponga , Fleurieu Peninsula and Mt. Painter, Flinders Ranges in South Australia and in the United States of America at San Juan in Colorado , at Spanish Fork in Utah and at Paria in the Orphan Mine in Arizona .
Precautions
Due to the high level of radioactivity and toxicity , mineral samples of uranospinite should only be kept in dust- and radiation-tight 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
- Uranospinites . 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; 65 kB ; accessed on January 5, 2018]).
- Mary E. Mrose: Studies of Uranium Minerals (XIII): Systhetic Uranospinites . In: American Mineralogist . tape 38 , 1953, pp. 1159–1168 ( minsocam.org [PDF; 645 kB ; accessed on January 5, 2018]).
Web links
- Mineral Atlas: Uranospinite (Wiki)
- Mindat - Uranospinite (English)
- Webmineral - Uranospinite (English)
Individual evidence
- ↑ a b c d e 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. 524 .
- ↑ a b c d e f g h i j k Uranospinites . 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; 65 kB ; accessed on January 5, 2018]).
- ↑ a b c d e f g h Mindat - Uranospinite (English)
- ^ A b c Mary E. Mrose: Studies of Uranium Minerals (XIII): Systhetic Uranospinites . In: American Mineralogist . tape 38 , 1953, pp. 1159–1168 ( minsocam.org [PDF; 645 kB ; accessed on January 5, 2018]).
- ↑ a b c Uranospinite in the type mineral catalog of the Mineralogical Museum of the University of Hamburg
- ↑ Richard V. Gaines, H. Catherine W. Skinner, Eugene E. Foord, Brian Mason , Abraham Rosenzweig: Dana's New Mineralogy . 8th edition. John Wiley & Sons, New York (et al.) 1997, ISBN 0-471-19310-0 , pp. 267 .
- ↑ a b Webmineral - Uranospinite (English)
- ↑ Find location list for uranospinite at the Mineralienatlas and at Mindat