Uranophane
| Uranophane | |
|---|---|
 |
|
| General and classification | |
| other names |
|
| chemical formula | Ca [UO 2 | SiO 3 OH] 2 • 5H 2 O |
|
Mineral class (and possibly department) |
Silicates and Germanates |
|
System no. to Strunz and to Dana |
9.AK.15 ( 8th edition : VIII / B.34) 53.03.01.02 |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic sphenoid; 2 |
| Space group | P 2 1 (No. 4) |
| Lattice parameters |
a = 15.91 (uranophane), 13.96 (uranophane-beta) Å ; b = 7.00 (uranophane), 15.44 (uranophane-beta) Å; c = 6.67 (uranophane), 6.33 (uranophane-beta) Å β = 97.3 (uranophane), 91.38 (uranophane-beta) ° |
| Formula units | Z = 2 |
| Frequent crystal faces | acicular, radial rays |
| Physical Properties | |
| Mohs hardness | 2 to 3, 2.5 to 3 |
| Density (g / cm 3 ) | 3.81 to 3.91 (measured), 3.78 (calculated) |
| Cleavage | completely after {100} |
| Break ; Tenacity | brittle |
| colour | light yellow to yellow green |
| Line color | light yellow |
| transparency | transparent to translucent |
| shine | Glass luster, pearlescent luster on split surfaces; earthy forms wax gloss to matt |
| radioactivity | very strong |
| Crystal optics | |
| Refractive indices |
n α = 1.643 (Uranophan), 1.660 to 1.678 (Uranophan-beta) n β = 1.666 (Uranophan), 1.682 to 1.723 (Uranophan-beta) n γ = 1.669 (Uranophan), 1.689 to 1.730 (Uranophan-beta) |
| Birefringence | δ = 0.026 (uranophane), 0.029 to 0.052 (uranophane-beta) |
| Optical character | biaxial negative (Uranophan and Uranophan-beta) |
| Axis angle | 2V = 32 ° to 45 ° (measured), 38 ° (calculated) (Uranophan), 42 ° to 58 ° (calculated) (Uranophan-beta) |
| Pleochroism | weak: x = colorless; y and z = light canary yellow (uranophane) |
| Other properties | |
| Special features | occasionally fluorescence |
The mineral uranophane (also uranotile ) is a frequently occurring island silicate of uranium with the chemical formula Ca [UO 2 | SiO 3 OH] 2 · 5H 2 O. It crystallizes in the monoclinic crystal system and usually develops needle-like crystals up to about 1 cm in size and radially radial , but also granular to massive mineral aggregates or crusty coatings of yellow to brown color.
Uranophane is known to crystallize in two different space groups as Uranophane-α ( Uranophane-alpha ) and Uranophane-β ( Uranophane-beta ). Both modifications are expressed in a different crystal habit , which, however, is often difficult to distinguish for the layman and only allows an assignment on closer inspection under the microscope.
Etymology and history
Uranophane was found for the first time in 1853 near Kupferberg (Tarnau) in Upper Silesia (Poland) and described by Martin Websky , who put the mineral according to its uranium content and the Greek word φαίνω [pronounced: "phanos"] for appear or appear, thus "appear like uranium" "named. Uranophan-beta was first recognized as such in 1935. The place where the mineral has its type locality is Jáchymov (St Joachimsthal) in Okres Karlovy Vary in the Ore Mountains in the Czech Republic.
Uranophane-α and Uranophane-β had already been discovered before the founding of the International Mineralogical Association (IMA) and recognized as separate mineral types. Therefore, this recognition was adopted by the IMA as grandfathered .
classification
In the now outdated, but still in use, 8th edition of the mineral classification according to Strunz , the uranophane belonged to the general department of "island silicates with non-tetrahedral anions ", where it named the "uranophane group" with system no. VIII / B.34 and the other members Boltwoodit , Cuprosklodowskit , Kasolit , Natroboltwoodit , Oursinit , Sklodowskit and Uranophan-beta.
Since the complete revision of Strunz's mineral classification in the 9th edition (2001), this section has been more precisely subdivided according to the absence or presence of further anions, the structure or the uranium: silicon ratio . The uranophane can be found accordingly in the department of “Uranyl island and polysilicates with the molar ratio U: Si = 2: 1”, where it forms the unnamed group 9.AK.15 together with boltwoodite, kasolite, natroboltwoodite and uranophane-beta .
The systematics of minerals according to Dana , which is common in English-speaking countries, also assigns uranophane to the island silicates department, but there in the department of " island silicates with SiO 4 groups and other anions and complex cations with (UO 2 ) ", where it is named Mineral the "uranophane group" with the system no. 53.03.01 forms.
Crystal structure
Uranophan-α crystallizes monoclinically in the space group P 2 1 (space group no. 4) with the lattice parameters a = 15.91 Å ; b = 7.00 Å; c = 6.67 Å and β = 97.3 ° and 2 formula units per unit cell .
Uranophan-β (or uranophan-beta ) also crystallizes monoclinically, but in the space group P 2 1 / a (No. 14, position 3) with the lattice parameters a = 13.97 Å ; b = 15.44 Å; c = 6.63 Å and β = 91.4 ° and 4 formula units per unit cell.
The figures below illustrate the different crystal lattices of the two Uranophane modifications.
Unit cell of uranophane-alpha in the direction of the crystallographic a-axis
__ U __ O __ Ca __ Si
__ water molecules
Packing pattern of uranophane-alpha in the direction of the crystallographic a-axis
__ U __ O __ Ca __ Si
__ water molecules
Unit cell of uranophane-beta in the direction of the crystallographic a-axis
__ U __ O __ Ca __ Si
__ water molecules
Packing image of uranophane-beta in the direction of the crystallographic c-axis
__ U __ O __ Ca __ Si
__ water molecules
properties
Uranophan is considered to be very radioactive due to its uranium content of up to 40.6% . Taking into account the proportions of the radioactive elements in the idealized empirical formula and the subsequent decays of the natural decay series, a specific activity of 72.5 k Bq / g is specified 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.
Occasionally uranophane can show a faint green fluorescence under UV light . Usually, however, the mineral is non-fluorescent.
Uranophane can easily be broken down by acids .
Modifications and varieties
(image width: 11, 5 mm)
Uranophan-alpha is dimorphic with uranophan-beta, which also crystallizes in the monoclinic crystal system, but in a different space group (see also structural data ).
Education and Locations
Uranophane is one of the most common uranium silicates. As a typical secondary mineral it forms in uranium - deposits and pegmatites by weathering of uraninite . In addition to uranophane beta, accompanying minerals include kasolite , autunite and meta-autunite , phosphuranylite , torbernite and various uranium oxides, but also calcite , malachite , almandine and muscovite .
Uranophane has been detected at more than 700 sites worldwide so far (as of 2010), including in Egypt , Algeria , Argentina , Australia , Brazil , China , Finland , Germany , France , India , Italy , Japan , Canada , Kazakhstan , Democratic ones Republic of the Congo , Madagascar , Mexico , Namibia , Norway , Austria , Poland , Portugal , Romania , Russia , Sweden , Switzerland , Slovakia , Spain , South Africa , Tajikistan , Tanzania , the Czech Republic , Hungary , Uzbekistan , the United Kingdom (Great Britain) and the United States of America (USA).
Particularly noteworthy are the locations of the Musonoi Mine near Kolwezi and Shinkolobwe Mine (Kasolo Mine) near Shinkolobwe in the Congolese province of Katanga , where crystals up to about 1 cm in size were found. Beautiful, radial-beam aggregates were recovered from the "Madawaska Mine (Faraday Mine)" near Bancroft in Hastings County (Canada).
use
Uranophan is as uranium - ore used.
Precautions
When handling the radioactive uranophane, sufficient radiation protection must be ensured. In order to prevent incorporation (absorption into the body), thorough hand washing is recommended after handling with bare hands.
See also
literature
- Paul Ramdohr , Hugo Strunz : Klockmann's textbook of mineralogy . 16th edition. Ferdinand Enke Verlag, 1978, ISBN 3-432-82986-8 , pp. 687 .
- Petr Korbel, Milan Novák: Encyclopedia of Minerals . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 211 .
- Uranophane-alpha , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 73.6 kB )
- Uranophane-beta , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 74.1 kB )
Web links
- Mineral Atlas: Uranophane (Wiki)
- Mineral Atlas: Uranophane Beta (Wiki)
Individual evidence
- ↑ a b c d e f Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 565 .
- ↑ a b Webmineral - Uranophane (English)
- ↑ a b c d e Mindat - Uranophane
- ↑ a b c d e Mindat - Uranophane-beta
- ^ FV Stohl, DK Smith, The crystal chemistry of the uranyl silicate minerals In: American Mineralogist 1981, Volume 66, S / 610-625. pdf, 1.6 MB (English)
- ↑ Web archive - "A dictionary of the names of minerals including their history and etymology"
- ^ IMA / CNMNC List of Mineral Names; September 2016 (PDF 1.6 MB; p. 189)
- ↑ File: Uranophane, Muscovite, Almandine - Pine Mountain, North Carolina, USA.jpg