Agrinierite
| Agrinierite | |
|---|---|
 |
|
| General and classification | |
| other names |
IMA 1971-046 |
| chemical formula |
|
|
Mineral class (and possibly department) |
Oxides and hydroxides |
|
System no. to Strunz and to Dana |
4.GB.05 ( 8th edition : IV / H.02) 05.05.01.01 |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-dipyramidal; 2 / m 2 / m 2 / m |
| Space group | Cmmm (No. 65) |
| Lattice parameters | a = 14.04 Å ; b = 24.07 Å; c = 14.13 Å |
| Formula units | Z = 16 |
| Twinning | pseudo-hexagonal rotation twins according to {110} |
| Physical Properties | |
| Mohs hardness | not defined |
| Density (g / cm 3 ) | measured: 5.7; calculated: [5.55] |
| Cleavage | good after {001} |
| colour | orange |
| Line color | Please complete |
| transparency | transparent to translucent |
| shine | Resin gloss, fat gloss |
| Crystal optics | |
| Refractive indices |
n α = not defined n β = 2.01 n γ = 2.06 |
| Optical character | biaxial negative |
| Axis angle | 2V = 55 ° |
Agrinierite is a very rarely occurring mineral from the mineral class of "oxides and hydroxides" with the idealized chemical composition K 2 Ca [(UO 2 ) 3 O 3 (OH) 2 ] 2 · 5H 2 O and is therefore chemically a potassium - Calcium - uranyl with additional hydroxide ions .
Agrinierite crystallizes in the orthorhombic crystal system and develops mostly tabular crystals that are flattened perpendicular to the c-axis and pseudo-hexagonal crystals due to the formation of twins . The surfaces of the transparent to translucent and orange-colored crystals have a resin-like to grease-like sheen .
Etymology and history
Agrinierite was first discovered together with Rameauit in the uranium mine of Margnac ("Mine de Margnac") in the French municipality of Compreignac . It was first described in 1972 by F. Cesbron, WL Brown, P. Bariand and J. Geffroy, who named the mineral after Henri Agrinier (1928–1971). As an engineer in the mineralogical laboratory of the French Atomic Energy Commission in Paris, he helped identify most of the uranium-containing minerals.
The type material of the mineral is kept at the University of Pierre and Marie Curie , at the Mines ParisTech ( École des mines de Paris ) in Paris , France and in the National Museum of Natural History in Washington, DC, USA (catalog no. 137454).
classification
In the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the agrinierite belonged to the mineral class of "oxides and hydroxides" and there to the department of "uranyl ([UO 2 ] 2+ ) -hydroxides and -hydrates", where he together with Rameauit formed the unnamed group IV / H.02 .
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 agrinierite to the class of "uranyl hydroxides". However, this is further subdivided according to the possible presence of additional cations and the structure of the uranyl complexes, so that the mineral is classified in the sub-section “With additional cations (K, Ca, Ba, Pb etc.); with predominantly UO 2 (O, OH) 5 pentagonal polyhedra "can be found, where together with Compreignacit and Rameauit the" Compreignacit group "with the system no. 4.GB.05 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the agrinierite to the class of "oxides and hydroxides" and there in the department of "uranium and thorium-containing oxides". Here he is to be found as the only member of the unnamed group 05.05.01 within the sub-section "Oxides containing uranium and thorium containing alkali and alkaline earth metal elements (containing water)".
Chemism
The chemical analysis of the material found gave an average composition of 2.05% SrO , 3.35% K 2 O , 2.20% CaO , 85.15% UO 3 and 7.45% H 2 0, which is the idealized oxide formula 2 (K 2 , Ca, Sr) O · 6UO 3 · 8H 2 O.
According to Strunz's crystal-chemical structural formula , the composition is given as (K 2 , Ca, Sr) [(UO 2 ) 3 | O 3 | (OH) 2 ] · 3H2O. The elements potassium , calcium and strontium indicated in round brackets can represent each other in the formula ( substitution , diadochy), but are always in the same proportion to the other constituents of the mineral.
After a new analysis of the structure by Christopher L. Cahill and Peter C. Burns, the empirical chemical composition was determined with K 2 (Ca 0.65 Sr 0.35 ) [(UO 2 ) 3 O 3 (OH) 2 ] 2 · 5H 2 O redefined and the idealized formula given as K 2 Ca [(UO 2 ) 3 O 3 (OH) 2 ] 2 · 5H 2 O.
Crystal structure
Agrinierite crystallizes orthorhombically in the space group Cmmm (space group no. 65) with the lattice parameters a = 14.04 Å ; b = 24.07 Å; c = 14.13 Å and 16 formula units per unit cell .
properties
The mineral is very radioactive due to its uranium content of up to 71.48% . 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 127.958 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.
Education and Locations
Agrinierite forms in the oxidation zone of uranium deposits and is accompanied by uranophane and gummite , among other things .
Apart from its type locality , the uranium mine of Margnac in France, no other locations for agrinierite are known (as of 2018).
See also
literature
- F. Cesbron, WL Brown, P. Bariand, J. Geffroy: Rameauite and Agrinierite, two new hydrated complex uranyl oxides from Margnac, France . In: Mineralogical Magazine . tape 38 , no. 299 , 1972, pp. 781–789 , doi : 10.1180 / minmag.1972.038.299.01 ( minersoc.org [PDF; 451 kB ; accessed on April 5, 2018]).
- Michael Fleischer : New Mineral Names . In: American Mineralogist . tape 58 , no. 7-8 , 1973, pp. 805-807 ( minsocam.org [PDF; 280 kB ; accessed on April 5, 2018]).
- Christopher L. Cahill, Peter C. Burns: The structure of agrinierite: a Sr-containing uranyl oxide hydrate mineral . In: American Mineralogist . tape 85 , 2000, pp. 1294–1297 ( rruff.info [PDF; 134 kB ; accessed on April 5, 2018]).
Web links
- Mineral Atlas: Agrinierite (Wiki)
- Mindat - Agrinierite (English)
- American-Mineralogist-Crystal-Structure-Database - Agrinierite (English)
Individual evidence
- ↑ a b c IMA / CNMNC List of Mineral Names; November 2017 (PDF 1.67 MB)
- ↑ a b c d 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. 250 .
- ↑ a b c Webmineral - Agrinierite (English)
- ↑ a b c d e f g h Agrinierite . 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; 69 kB ; accessed on April 1, 2018]).
- ↑ F. Cesbron, WL Brown, P. Bariand, J. Geffroy: Rameauite and Agrinierite, two new hydrated complex uranyl oxides from Margnac, France . In: Mineralogical Magazine . tape 38 , no. 299 , 1972, pp. 785 , doi : 10.1180 / minmag.1972.038.299.01 ( minersoc.org [PDF; 451 kB ; accessed on April 5, 2018]).
- ↑ Christopher L. Cahill, Peter C. Burns: The structure of agrinierite: a Sr-containing uranyl oxide hydrate mineral . In: American Mineralogist . tape 85 , 2000, pp. 1294–1297 ( rruff.info [PDF; 134 kB ; accessed on April 5, 2018]).
- ↑ Find location list for agrinierite at the Mineralienatlas and at Mindat