Ianthinite
| Ianthinite | |
|---|---|
 |
|
| General and classification | |
| chemical formula | U 4+ 2 [(UO 2 ) 4 | O 6 | (OH) 4 ] • 9H 2 O |
|
Mineral class (and possibly department) |
Oxides and hydroxides |
|
System no. to Strunz and to Dana |
4.GA.10 ( 8th edition : IV / F.11) 06/05/01/01 |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-pyramidal; mm 2 |
| Space group | P 2 1 cn (No. 33, position 4) |
| Lattice parameters | a = 7.178 Å ; b = 11.473 Å; c = 30.39 Å |
| Formula units | Z = 4 |
| Physical Properties | |
| Mohs hardness | 2 to 3 |
| Density (g / cm 3 ) | calculated: 5.24 |
| Cleavage | completely after {001} |
| Break ; Tenacity | uneven |
| colour | purple, black |
| Line color | brown, purple |
| transparency | translucent |
| shine | Metal luster, glass luster |
| radioactivity | very strong |
| Crystal optics | |
| Refractive indices |
n α = 1.674 n β = 1.900 n γ = 1.920 |
| Birefringence | δ = 0.246 |
| Optical character | biaxial negative |
| Axis angle | 2V = 58 ° (measured); 30 ° (calculated) |
| Pleochroism | visible: X = c = colorless Y = b = violet Z = a = dark purple |
Ianthinite is a rather seldom occurring uranium mineral from the mineral class of " oxides and hydroxides ". It crystallizes in the orthorhombic crystal system with the chemical composition U 4+ 2 [(UO 2 ) 4 | O 6 | (OH) 4 ] · 9H 2 O and develops mostly dark purple, shiny metallic crystals with a needle-like habit . In Ianthinit the uranium is used both in the oxidation state +6 and in the oxidation state +4. Due to the instability of the +4 oxidation state to atmospheric oxygen, the violet needles slowly weather and therefore often show a yellow coating of schoepite ([(UO 2 ) 4 | O | (OH) 6 ] · 6H 2 O) or metaschoepite ((UO 3 ) · NH 2 O n≈2).
Etymology and history
Ianthinite was first discovered in 1926 by Alfred Schoep in the Shinkolobwe Mine (Kasolo Mine) in the Katanga province, which is now part of the Democratic Republic of the Congo (Zaire) . It got its name from the Greek word ianthinos ( ancient Greek ἰάνθινος ) for 'violet'.
classification
Already in the 8th edition of the mineral classification according to Strunz , which has been obsolete since 1977 , the ianthinite belonged to the mineral class of "oxides and hydroxides" and there to the department of "hydroxides", where it was named after the "Ianthinit series" with the system no. IV / F.11 and the other member Masuyit .
In the Lapis mineral directory according to Stefan Weiß, which, out of consideration for private collectors and institutional collections, is still based on this classic system of Karl Hugo Strunz , the mineral was given the system and mineral number. IV / H.01-10 . In the "Lapis system" this also corresponds to the class of "oxides and hydroxides", but there the department "Uranyl ([UO 2 ] 2+ ) hydroxides and hydrates", where ianthinite together with studtite , metastudtite , schoepite , Metaschoepite , Paulscherrerite , Heisenbergite and Paraschoepite (mineral status doubtful) forms an independent but unnamed group (as of 2018).
The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and was updated by the International Mineralogical Association (IMA) until 2009, also classifies Ianthinite in the “uranyl hydroxide” department. However, this is further subdivided according to the possible presence of further cations , so that the mineral can be found according to its composition in the sub-section “Without additional cations”, where it is the only member of the unnamed group 4.GA.10 .
The systematics of minerals according to Dana also assigns the ianthinite to the class of "oxides and hydroxides", but there in the category of "uranium and thorium-containing oxides". Here he is to be found as the only member of the unnamed group 05.06.01 within the subdivision " Oxides containing uranium and thorium with polyvalent uranium ".
Crystal structure
Ianthinite crystallizes orthorhombically in the space group P 2 1 cn (space group no. 33, position 4) with the lattice parameters a = 7.178 Å ; b 11.473 Å and c 30.39 Å as well as 4 formula units per unit cell .
In its structure, Ianthinite contains both uranium in the +6 oxidation state (in the form of the uranyl ion UO 2 2+ ) and in the +4 oxidation state (U 4+ ). The uranyl ions show classic pentagonal-bipyramidal coordination, with the uranyl oxygen atoms representing the tips of the pyramid and oxide (O 2− ) or hydroxide ions (OH - ) being coordinated in equatorial positions . The U 4+ ions, on the other hand, have a distorted octahedral coordination. These uranium polyhedra are linked to one another via oxygen atoms (made up of O 2− , OH - and H 2 O) and form layers that are held together by the water of crystallization by means of hydrogen bonds . The by Peter Burns et al. Formula [U 4+ 2 (UO 2 ) 4 O 6 (OH) 4 (H 2 O) 4 ] (H 2 O) 5 determined in 1997 on the basis of a single crystal structure analysis separates the water molecules found: there are four water molecules (within the square brackets) within the layers, five water molecules are between the layers and hold them together. The crystal structure analysis also shows that in some areas of the crystal lattice the uranium (IV) is already partially oxidized to uranium (V) or uranium (VI).
Due to the presence of U 4+ ions, Ianthinite is also considered as a model structure for the oxidative dissolution of spent nuclear fuel, since the Pu 4+ ions, which are very similar due to the ion radius, bond lengths with oxygen and chemical valency, theoretically form the lattice sites of the U 4+ - Could ingest ions.
Ianthinite - packing pattern in the direction of the crystallographic a-axis ( __ U __ O __ water molecules )
Ianthinite - packing pattern in the direction of the crystallographic b-axis ( __ U __ O __ water molecules )
properties
Ianthinite is relatively highly radioactive due to its uranium content of up to 78.3 % by weight . Taking into account the natural decay series, a specific activity of about 140.1 k Bq / g is given for ianthinite (for comparison: natural potassium 0.0312 kBq / g).
The mineral is unstable in the air and changes to schoepit or metaschoepit through oxidation .
Education and Locations
Ianthinite occurs in paragenesis with uranyl oxide hydrates such as Becquerelit and Vandendriesscheit . It is practically always associated with primary uraninite and also occurs together with uranyl carbonates such as rutherfordin and wyartite . The formation of ianthinite is, however, relatively poorly understood. Ianthinite could be formed by incomplete oxidation of uraninite, however the laboratory synthesis of ianthinite from solution requires a partial reduction of uranium (VI). The association of Ianthinite with carbonatic minerals seems to give indications that anaerobic or weakly reducing environments promote the formation of the mineral. Other minerals associated with ianthinite are kasolite , parsonsite , dewindtite and fourmarierite .
By far the most important paragenesis is that with schoepit , metaschoepit and paraschoepit due to the instability of the +4 oxidation state of uranium in ianthinite. In 1999, Walenta describes the observed transformation of a mineral sample from Ianthinite to Schoepit from the Clara pit from 1997. At the time of the discovery, the 1.5 mm long crystals were largely preserved as Ianthinite and only showed transformations at the edges of the mine Crystals, whereas Walenta was only able to detect ianthinite in places in the same mineral sample after less than two years.
In addition to its type locality "Shinkolobwe Mine", the mineral also appeared in the Democratic Republic of the Congo in the Musonoi mine near Kolwezi and in the Swambo mine .
In Germany, Ianthinite was found in the Krunkelbach mine near Menzenschwand and in the Clara mine near Oberwolfach in Baden-Württemberg. Other sites in Germany are Schwandorf in Bavaria and Mähring in the Upper Palatinate Forest.
Other locations are in Australia, France, Italy, Mexico, Slovakia and the USA.
Precautions
Due to the toxicity and the strong radioactivity of the mineral, mineral samples of Ianthinit 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
Web links
- Mineral Atlas: Ianthinite (Wiki)
- American-Mineralogist-Crystal-Structure-Database - Ianthinite. In: rruff.geo.arizona.edu. Retrieved October 7, 2019 .
- Photos from Ianthinit on the website of the Association des Géologues Amateurs de Belgique (AGAB). In: agab.be. February 14, 2007, accessed October 7, 2019 .
Individual evidence
- ^ A b 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. 249 (English).
- ↑ a b c Malcolm Back, William D. Birch, Michel Blondieau and others: The New IMA List of Minerals - A Work in Progress - Updated: September 2019. (PDF 2672 kB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, September 2019, accessed October 11, 2019 .
- ^ A b c David Barthelmy: Ianthinite Mineral Data. In: webmineral.com. Retrieved October 7, 2019 .
- ↑ a b c d e f Peter C. Burns, Robert J. Finch, Frank C. Hawthorne, Mark L. Miller, Rodney C. Ewing: The crystal structure of ianthinite, [U 4+ 2 (UO 2 ) 4 O 6 (OH) 4 (H 2 O) 4 ] (H 2 O) 5 : a possible phase for Pu 4+ incorporation during the oxidation of spent nuclear fuel . In: Journal of Nuclear Materials . tape 249 , 1997, pp. 199-206 , doi : 10.1016 / S0022-3115 (97) 00212-2 (English).
- ↑ a b c d e f g h Ianthinite. In: mindat.org. Hudson Institute of Mineralogy, accessed October 7, 2019 .
- ^ A b Robert J. Finch, Frank C. Hawthorne, Rodney C. Ewing: Structural relations among schoepite, metaschoepite, and "dehydrated schoepite" . In: The Canadian Mineralogist . tape 36 , 1998, pp. 831–845 (English, rruff.info [PDF; 2.0 MB ; accessed on October 7, 2019]).
- ↑ a b c Ianthinite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 (English, handbookofmineralogy.org [PDF; 72 kB ; accessed on October 7, 2019]).
- ↑ Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties. Status 03/2018 . 7th, completely revised and supplemented edition. Weise, Munich 2018, ISBN 978-3-921656-83-9 .
- ↑ Ernest H. Nickel, Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF 1703 kB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed October 11, 2019 .
- ↑ Kurt Walenta: New mineral finds from the Clara mine . In: Lapis mineral magazine . tape 24 , no. 11 , 1999, p. 34-38 .