Sklodovskite
| Sklodovskite | |
|---|---|
 |
|
| General and classification | |
| other names |
Chinkolobwit |
| chemical formula | Mg (H 3 O) 2 [(UO 2 ) 2 (SiO 4 ) 2 ] • 4H 2 O |
|
Mineral class (and possibly department) |
Silicates and Germanates |
|
System no. to Strunz and to Dana |
9.AK.10 ( 8th edition : VIII / B.34) 53.03.01.03 |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic; 2 / m |
| Space group | C 2 / m (No. 12) |
| Lattice parameters |
a = 17.382 Å ; b = 7.047 Å; c = 6.610 Å, α = 90.00 °; β = 105.90 °; γ = 90.00 ° |
| Formula units | Z = 2 |
| Frequent crystal faces | needle-like along {010} |
| Twinning | with {001} or {100} as twin levels |
| Physical Properties | |
| Mohs hardness | 2 to 3 |
| Density (g / cm 3 ) | 3.54 |
| Cleavage | completely after {100} |
| Break ; Tenacity | brittle |
| colour | greenish yellow, light yellow |
| Line color | yellow white |
| transparency | translucent to partially translucent |
| shine | Glass gloss, wax gloss, silk gloss, diamond gloss |
| radioactivity | very strong |
| Crystal optics | |
| Refractive indices |
n α = 1.613 to 1.615 n β = 1.635 to 1.642 n γ = 1.656 to 1.657 |
| Birefringence | δ = 0.043 to 0.044 |
| Optical character | biaxial negative |
| Pleochroism | X = colorless; Y = yellow; Z = light yellow |
| Other properties | |
| Chemical behavior | soluble in hydrochloric acid |
The mineral Sklodowskit is a rather seldom occurring uranium mineral with the chemical composition Mg (H 3 O) 2 [(UO 2 ) 2 (SiO 4 ) 2 ] · 4H 2 O. It crystallizes in the monoclinic crystal system and develops mostly acicular, radial pale yellow to yellow crystals . Chemically, it is a magnesium - uranyl - silicate .
Etymology and history
Sklodowskite was first described in 1924 by Alfred Schoep on a mineral sample from the Shinkolobwe mine in what is now the Democratic Republic of the Congo. He named it in honor of Marie Curie , who kept her maiden name Skłodowska in her name after she married Pierre Curie . However, the Polish letter " ł " was transcribed by the Latin letter " l ". A short time later, Schoep published a further study on the mineral he had newly discovered and described its similarities with uranotil ( uranophane ). His analysis showed that the Sklodovskite can be regarded as " Magnesium Uranophane " or the Uranophane as " Calcium Sklodowskite ". The different crystal modifications of uranophane known today make this statement seem justified only with regard to the chemistry.
classification
The outdated 8th edition of the Strunz lists the Sklodowskite in the "Uranophangruppe" with the system no. VIII / B.34 and the other members boltwoodite , cuprosklodovskite , kasolite , natroboltwoodite , oursinite , uranophane and uranophane-beta .
The 9th, completely revised edition of Strunz lists the Sklodowskite in the section K "Uranyl island and polysilicates with a uranium: silicon ratio of U: Si = 2: 1" in group 9.AK.10 . This group also includes cuprosklodovskite and ourinite.
The systematics of minerals according to Dana , which is common in English-speaking countries , assigns the Sklodovskite to the uranophane group of the island silicates department, but there in the department of " island silicates with SiO 4 groups and other anions as well as complex cations with (UO 2 ) " with the system No. 53.03.01.03 a.
Crystal structure
Sklodovskite crystallizes in the monoclinic space group C 2 / m (space group no. 12) with the lattice parameters a = 17.382 Å ; b = 7.047 Å; c = 6.610 Å with α = 90.00 ° β = 105.90 ° and γ = 90.00 ° as well as two formula units per unit cell .
The crystal structure of Sklodowskit shows uranyl-silicate layers, which are connected to each other by magnesium ions. The Mg 2+ ion is coordinating two opposite SiO 4 tetrahedra (∠ (SiO-Mg) = 146.18 °, ∠ (O-Mg-O) = 180 °), and forms, by coordinating four crystal water molecules a octahedral coordination polyhedra . The uranyl ion has a pentagonal-bipyramidal coordination environment, with the five equatorial oxygen atoms coming from four different silicate groups. Of the four silicate oxygen atoms, the first coordinates to the magnesium atom, the second coordinates simply to a uranyl unit and the third and fourth coordinate three further uranyl units in such a way that one uranyl unit coordinates twice, i.e. once from the third and once from the fourth silicate oxygen atom becomes.
properties
The mineral is radioactive due to its uranium content of up to 55.4% . 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 99.2 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
Sklodovskite occurs in the weathering zone of primary uranium ores. It forms in silicate-rich zones after the formation of oxide and hydroxide minerals, but before the crystallization of phosphates. It is found together with kasolite , soddyite , torbernite , uranophane , novacekite , metazeunerite and curite . In addition to its type locality , the Shinkolobwe Mine , Sklodowskite is also found in the Musonoi Mine , in Kamoto , Swambo Hill , Kasompi and Luiswishi in the Democratic Republic of the Congo . In Germany it is known from Tirpersdorf , Ronneburg and from the Bühlskopf deposit in Ellweiler . In Switzerland it was found in La Creusaz . In France it was found in Rabejac near Lodève in the Hérault department in the Occitania region . In the Czech Republic it is known from Jáchymov , among others . Sklodovskite is found in more than fifteen mines in the United States. Other isolated sites are in Australia, Brazil, China, Canada, Mexico, New Zealand and Tajikistan.
Precautions
Due to the toxicity and radioactivity of the mineral, mineral samples from the Sklodovskite should only be kept in dust- and radiation-proof 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
- Sklodowskite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 73.2 kB )
Web links
- Mineral Atlas: Sklodovskite (Wiki)
Individual evidence
- ^ A b c DH Gorman: Studies of radioactive compounds, IX - sklodowskite In: The Canadian Mineralogist 1957, 6, pp. 52-60. (English, PDF, 594 kB)
- ↑ a b FV Stohl, DK Smith: The crystal chemistry of the uranyl silicate minerals In: American Mineralogist 1981, 66, pp. 610–625, (English, PDF, 1.6 MB)
- ↑ a b c d e f g Webmineral - Sklodowskite (English)
- ↑ a b Mindat - Sklodowskite (English)
- ↑ a b A. Schoep: Sur la sklodowskite, nouveau minéral uranifère; ses analogies avec l'uranotile In: Bulletin de la Société Française de Minéralogie 1924, 47, pp. 162-172. (French, PDF, 488 kB)
- ↑ A. Schoep: La sklodowskite, nouveau minéral radioactif In: Comptes Rendus de l'Académie des sciences in 1924 (T179), pp 413-415. (French, online)