Marthocite
| Marthocite | |
|---|---|
 |
|
| General and classification | |
| chemical formula | Cu (UO 2 ) 3 (SeO 3 ) 2 O 2 · 8H 2 O |
|
Mineral class (and possibly department) |
Oxides and hydroxides |
|
System no. to Strunz and to Dana |
4.JJ.05 ( 8th edition : IV / K.11) 07/34/04/01 |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-pyramidal mm 2 |
| Room group (no.) | Pbn 2 1 (No. 33) |
| Lattice parameters | a = 16.4537 Å ; b = 17.2229 Å; c = 6.9879 Å |
| Formula units | Z = 4 |
| Physical Properties | |
| Mohs hardness | 6th |
| Density (g / cm 3 ) | 4.44 |
| Cleavage | completely after {100}, indistinct after {010} |
| colour | yellowish green to greenish brown |
| Line color | yellow |
| transparency | translucent to opaque |
| shine | Please complete |
| radioactivity | very strong |
| Crystal optics | |
| Optical character | biaxial negative |
| Axis angle | 2V = measured: 39 ° |
| Pleochroism | X = yellowish brown; Y = Z = greenish yellow |
Marthozite is a very rare occurring uranium - mineral from the mineral class of "oxides and hydroxides" (including V [5,6] -Vanadate, Arsenites, Antimonite, Bismutite, sulfites, Selenite, tellurites and iodates). It crystallizes in the orthorhombic crystal system with the chemical composition Cu (UO 2 ) 3 (SeO 3 ) 2 O 2 · 8H 2 O, so it is a water-containing copper - uranyl - selenite .
Marthozite often develops yellow-green, pyramidal crystals and yellow aggregates.
Etymology and history
Marthozite was first discovered on a mineral sample from the Musonoi mine in Katanga (today: Democratic Republic of the Congo ) and described in 1969 by Fabien Cesbron, Robert Oosterbosch and Roland Pierrot, who named the mineral after the French mineralogist Aime Marthoz (1864–1962).
The empirical formula Cu (UO 2 ) 3 (SeO 3 ) 3 (OH) 2 7H 2 O was initially given by the first person describing it . In 2001, single crystal structure analysis resulted in Cu (UO 2 ) 3 (SeO 3 ) 2 O 2 8H 2 O Getting corrected.
The type mineral is stored under catalog number 12.252 in the Natural History Museum in Paris .
classification
The outdated 8th edition of the Strunz lists the marthocite under "Uranylselenite with assemblies [UO 2 ] 2+ to [SeO 3 ] 2− " with the system no. IV / K.11 together with Demesmaekerit , Derriksit , Guilleminit , Haynesit , Larisait and Piretit .
The 9th, completely revised edition of Strunz lists the marthocite in Section J “ Selenite with additional anions; with H 2 O “as the only representative of the group 4.JJ.05 .
The systematics of minerals according to Dana , which is common in the English-speaking world , assigns the marthocite to the selenites - tellurites - sulphites within the sulphates, chromates and molybdates with the system number. 07/34/04/01 a.
Crystal structure
Marthocite crystallizes in the orthorhombic crystal system in the space group Pbn 2 1 (space group no. 33) with the lattice parameters a = 16.4537 Å ; b = 17.2229 Å; c = 6.9879 Å and 4 formula units per unit cell .
The crystal structure of marthocite has three different uranyl units, one of which is hexagonal-bipyramidal, the other two pentagonal-bipyramidal are surrounded by oxygen atoms. The selenite units form trigonal pyramids with the selenium atom as a tip. This creates layers of uranyl cations and selenite anions, which are bridged to one another by the Cu 2+ ions. However, the copper ions coordinate exclusively the pentagonal-bipyramidal uranyl units. The copper itself is surrounded by four units of crystal water, so that it is octahedral surrounded by six oxygen atoms.
Layer structure of marthozite in the direction of the crystallographic a-axis ( __ U __ O __ Se __ Cu __ water molecules )
properties
The mineral is radioactive due to its uranium content of up to 54.78% . Taking into account the proportions of the radioactive elements in the idealized empirical formula as well as the subsequent decays of the natural decay series, a specific activity of about 98 k Bq / g is given for the mineral (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.
Modifications and varieties
Cesbron, Oosterbosch and Pierrot as well as Cooper and Hawthorn report a meta-form of marthozite. The work of the latter authors gives a molecular formula of Cu (UO 2 ) 3 (SeO 3 ) 2 O 2 · 6H 2 O for metamarthocite . It also crystallizes orthorhombically with similar cell dimensions, with only the b axis being shortened to 15.8 Å.
Education and Locations
Marthocite forms as a secondary uranium mineral in the oxidation zone of selenium-rich hydrothermal uranium ores. It is found in association with Digenit , Demesmaekerit , Denningit , Guilleminit . In addition to the type locality in the Kasolo mine near Kolwezi , marthozite can only be found worldwide in "La Creusaz U prospect" in Les Marécottes in the canton of Valais in Switzerland and possibly in Moldava near Dubí in the Czech Republic .
Precautions
Due to the strong radioactivity of the mineral, mineral samples of marthocite should only be kept in dust- and radiation-tight containers, but especially never in living rooms, bedrooms or workrooms. Likewise, because of the high toxicity and radioactivity of uranyl compounds, absorption into the body ( incorporation , ingestion ) should be prevented in any case and, for safety, direct body contact should be avoided and face masks and gloves should be worn when handling the mineral.
See also
literature
- Marthozite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 71.4 kB )
Web links
- Mineral Atlas: Marthozite
- Photos of Marthozit on the website of the Association des Géologues Amateurs de Belgique (AGAB)
Individual evidence
- ^ A b c d Mark A. Cooper, Frank C. Hawthorne: Structure topology and hydrogen bonding in marthozite, Cu 2+ [(UO 2 ) 3 (SeO 3 ) 2 O 2 ] (H 2 O) 8 , a comparison with guilleminite, Ba [(UO 2 ) 3 (SeO 3 ) 2 O 2 ] (H 2 O) 3 . In: The Canadian Mineralogist. 2001, Volume 39, pp. 797-807. ( PDF, 522 kB (English)).
- ↑ a b c d e Marthozite at Webmineral.com .
- ↑ a b c Marthozite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 71.4 kB ).
- ^ Fabien Cesbron, R. Oosterbosch, Roland Pierrot: Une nouvelle espèce minérale: la marthozite. Uranyl selenite de cuivre hydrate. In: Bulletin de la Société Française de Minéralogie et de Cristallographie. 1969, Volume 92, pp. 278-283 ( PDF, 294 kB (French) ).
- ↑ a b Mindat - Marthozite .