Bassetite
| Bassetite | |
|---|---|
 |
|
| General and classification | |
| chemical formula | Fe 2+ (UO 2 ) (PO 4 ) 2 • 8H 2 O |
|
Mineral class (and possibly department) |
Phosphates, arsenates and vanadates |
|
System no. to Strunz and to Dana |
8.EB.10 ( 8th edition : VII / E.02) 40.2a.16.01 |
| Crystallographic Data | |
| Crystal system | Monoclinic |
| Crystal class ; symbol | Monocline prismatic, 2 / m |
| Space group | P 2 1 / m (No. 11) |
| Lattice parameters |
a = 6.98 Å ; b = 17.07 Å; c = 7.01 Å β = 90.32 ° |
| Formula units | Z = 2 |
| Frequent crystal faces | {111}, {101}, {110}, {001}, {010} |
| Twinning | Frequently; two or more twins on [001] or one twin parallel to [100]; |
| Physical Properties | |
| Mohs hardness | 2.5 |
| Density (g / cm 3 ) | calculated: 3.63; measured: 3.40 to 3.63 |
| Cleavage | Perfect at {010}; Partly to {100} and {001} |
| Break ; Tenacity | brittle |
| colour | yellow-brownish |
| Line color | light yellow to greenish white |
| transparency | transparent |
| shine | Glass gloss |
| radioactivity | available |
| Crystal optics | |
| Optical character | Biaxial (likely) |
| Axis angle | 2V = 90 ° |
| Pleochroism | X = Y = yellow, Z = dark olive brown to brown-black |
| Other properties | |
| Chemical behavior | soluble in acids |
Bassetite is a rare mineral from the mineral class of phosphates , arsenates and vanadates . It crystallizes in the monoclinic crystal system with the chemical composition Fe 2+ (UO 2 ) (PO 4 ) 2 • 8H 2 O. The transparent crystals are yellow to brownish-yellow in color, also greenish-brown to olive-green in color with a greenish-white streak color and have a surface glass-like sheen.
Etymology and history
The mineral was discovered by Arthur Francis Hallimond in 1915 in the Bissit Mining Group, Cornwall , England , UK . He named it in honor of the type locality (place of the first description) Bassitit (in English Bassitite ). The mineral has been confirmed by the International Mineralogical Association (IMA) as being described prior to its inception and therefore counts as grandfathered . The type mineral is kept at Harvard University in Cambridge , Massachusetts, USA , the Natural History Museum in London , England and the technical university " Mines ParisTech ", Paris in France.
classification
Already in the outdated, but partly still in use 8th edition of the mineral systematics according to Strunz , the bassetite belonged to the mineral class of "phosphates, arsenates and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 abernathyite , chernikovite , Lehnerit , Metaankoleit , Metaautunit , Metaheinrichit , Metakahlerit , Metakirchheimerit , Metalodèvit , Metanatroautunit (meta-sodium Autunit) Metanováčekit , Metatorbernit , Metauranocircit , Metauranospinit , Metazeunerit , Natrouranospinit , Pseudoautunit , Ulrichit , Uramarsit and Uramphit the "Metaautunit group" with the System number VII / E.02 formed.
The 9th edition of Strunz's mineral systematics, which has been in effect since 2001 and is used by the IMA, classifies the bassetite in the now abbreviated section of “uranyl phosphates and arsenates”. However, this is further subdivided according to the chemical structure, so that the mineral according to its composition in the sub-section "with [UO 2 ] 2+ - [PO 4 ] / [AsO 4 ] 3− and [UO 2 ] 2+ - [V 2 O 8 ] 6− as well as isotype vanadate ( sincosit series) ”, where it can be found again in the“ Metaautunit group ”. This consists - unchanged - in addition to bassetite of abernathyite, chernikovite, lehnerite, metaankoleit, metaautunite, metaheinrichite, metakahlerite, metakirchheimerite, metalodèvite, metanatroautunit (meta-sodium autunite), metanováčekite, metauranospunite, metauranospunite, metauranospunite, metauranospunite, Ulrich , Uramarsite and Uramphite.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the bassetite to the class of “phosphates, arsenates and vanadates” and there to the category of “hydrous phosphates etc., with A 2+ (B 2+ ) 2 (XO 4 ) • x (H 2 O), with (UO 2 ) 2+ “a. Here it is in the unnamed group with the system number 40.02a.16 with the system no. 40.02a.16.01 to find.
Chemism
The UO 2 is not stored uranium (IV) oxide , but is based on a U 6+ cation, the so-called uranyl . With two positive charges, it balances the phosphate anion (three times negative) on the remaining two times negative, which are ultimately neutralized by iron . A synthesis of Bassetite by Vochen, de Grave and Pelsmaekers from 1984 is based on the "Hydrogen Autunit" (English Hydrogen autunite ), which has the formula H [UO 2 | PO 4 ]. In this notation, the Bassetite formula can also be written as Fe 2+ [UO 2 | PO 4 ] 2 .
Crystal structure
Bassetite crystallizes monoclinically in the space group P 2 1 / m (space group no. 11) with the lattice parameters a = 6.98 Å , b = 17.07 Å and c = 7.01 Å and two formula units per unit cell .
properties
morphology
Bassetite forms crystals with a square or rectangular contour. They are up to 3 mm in size.
Chemical properties
Bassetite is soluble in acids .
Physical Properties
Due to its uranium content of up to 51.19%, the mineral is very radioactive . Taking into account the natural series of decay or any decay products present, the specific activity is given as 91.63 k Bq / g (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.
Education and Locations
Bassetite forms parageneses with chemically related minerals. It was Uranospathit , Torbernit , uraninite , pyrite observed Metaautunit, Saléeit and Metanováčekit.
In general, bassetite is a rather rare mineral. Nevertheless, it can be found in some places: In Brazil , China , Germany , France , Gabon , Great Britain, Italy , Canada , Poland , Spain , Switzerland , the Czech Republic and in the USA .
Precautions
Due to the toxicity and the high level of radioactivity of the mineral, mineral samples from bassetite should only be kept in dust- and radiation-tight containers, but especially never in living rooms, bedrooms or workrooms. 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
- C. Frondel: Systematic mineralogy of uranium and thorium In: US Geological Survey Bulletin , Vol. 1064, 1958, pp. 200-204.
- R. Vochen, E. de Grave, J. Pelsmaekers: Mineralogical study of bassetite in relation to its oxidation In: American Mineralogist , Vol. 69, 1984, pp. 967-978 ( PDF )
- R. Vochen, G. Brizzi: Bassetite and other uranium minerals from Arcu su Linnarbu, Capoterra, Cagliari, Sardinia In: Mineralogical Reports , Vol. 18, 1987, pp. 181-184
Web links
Individual evidence
- ↑ a b c d e f g h Bassetite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 59 , 7 kB )
- ↑ a b c d e Bassetite at Mindat
- ↑ a b Mineralienatlas: Bassetit
- ↑ R. Vochten, E. de Grave, J. PELSMAEKERS: Mineralogical study of bassetite in relation to its oxidation- In: American Mineralogist ., Vol 69, 1984, pp 967-978 ( PDF , English)
- ↑ a b Webmineral - Bassetite