Schröckingerit
| Schröckingerit | |
|---|---|
 |
|
| General and classification | |
| chemical formula | NaCa 3 [(UO 2 ) (CO 3 ) 3 (SO 4 ) F] • 10H 2 O |
|
Mineral class (and possibly department) |
Carbonates and nitrates (formerly carbonates, nitrates and borates) |
|
System no. to Strunz and to Dana |
5.EG.30 ( 8th edition : VI / D.21) 01/17/05/01 |
| Crystallographic Data | |
| Crystal system | triclinic |
| Crystal class ; symbol | triclinic pinacoidal; 1 |
| Space group | P 1 (No. 2) |
| Lattice parameters |
a = 9.634 (1) Å ; b = 9.635 (1) Å; c = 14.391 (2) Å α = 91.41 (1) °; β = 92.33 (1) °; γ = 120.26 (1) ° |
| Formula units | Z = 2 |
| Physical Properties | |
| Mohs hardness | 2.5 |
| Density (g / cm 3 ) | measured: 2.51 |
| Cleavage | completely after {001} |
| colour | greenish yellow, light green |
| Line color | yellowish white |
| transparency | transparent |
| shine | Pearlescent |
| radioactivity | very strong |
| Crystal optics | |
| Refractive indices |
n α = 1.495 n β = 1.543 n γ = 1.544 |
| Birefringence | δ = 0.049 |
| Optical character | biaxial negative |
| Axis angle | 2V = 16 ° |
| Pleochroism | X = colorless, pale yellow; Y = Z = greenish yellow |
| Other properties | |
| Special features | Fluorescence in short-wave (254 nm) and long-wave (366 nm) UV light |
Schröckingerite is a rarely occurring mineral from the mineral class of " carbonates and nitrates " (formerly "carbonates, nitrates and borates "). It crystallizes in the trigonal crystal system with the chemical composition NaCa 3 [(UO 2 ) (CO 3 ) 3 (SO 4 ) F] · 10H 2 is O and chemical point of view, a sulfate -, fluoride - and hydrous sodium - calcium - uranyl carbonate .
Schröckingerite rarely develops good crystals and often forms pale green, crusty aggregates of fine crystal flakes.
Schröckingerite fluoresces greenish-yellow under short-wave (254 nm) and long-wave (366 nm) UV light .
Etymology and history
Schröckingerite was first described by Albrecht Schrauf in 1873 . He received from Julius Freiherr von Schröckinger von Neudenberg (1813–1882) a collection of various minerals from Joachimsthal (today: Jáchymov ), on which he found pearlescent, 1 mm crystal flakes in the form of spherical or flake-like aggregates of light greenish-yellow color on uraninite . He named it "Schröckingerit" after Baron Schröckinger.
The type material is kept in the Natural History Museum in Vienna .
classification
In the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the Schröckingerite belonged to the common mineral class of "sulfates, chromates, molybdates, tungstates" and there to the department of "water-containing sulfates with foreign anions", where together with deliensite , Johannit and pseudojohannit formed the Johannit group VI / D.21 .
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 Schröckingerite to the newly defined class of “carbonates and nitrates” and there to the “uranyl carbonates” category. In this it is in the subdivision of uranyl carbonates with sulphate (SO42-) or silicate (SiO44-) forms under the system number 5.EG.05 .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Schröckingerite, like the outdated Strunz system, to the common class of “carbonates, nitrates and borates” and there to the division of “hydrous carbonates”. Here he is to be found as the only member of the unnamed group 01/17/05 within the sub-section “ Compound carbonates with different formulas”.
Crystal structure
Schröckingerite crystallizes triclinically in the space group P 1 (space group no.2 ) with the lattice parameters a = 9.634 (1) Å , b = 9.635 (1) Å, c = 14.391 (2) Å, the axis angles α = 91.41 (1) °, β = 92.33 (1) °, γ = 120.26 (1) ° and 2 formula units per unit cell .
The crystal structure of Schröckingerit is a very complex system, the basic motif of which is uranyl carbonate , which builds up layers through coordination with Ca 2+ and Na + ions, which are interconnected by sulfate anions (SO 4 2− ) and a network of hydrogen bonds be held together. The fluoride ions (F - ) only bridge three calcium ions.
properties
The mineral is radioactive due to its uranium content of up to 26.8% . Taking into account the proportions of radioactive elements in the idealized empirical formula as well as the subsequent decays of the natural decay series , a specific activity of about 48 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 composition of the levels; selective enrichment or depletion of the radioactive decay products is also possible and changes the activity.
Education and Locations
Schröckingerite occurs as a rather rare secondary mineral in the oxidation zone of uranium-containing deposits. As Begleitminerale among others can Albrechtschraufit , Andersonit , Bayleyit , dolomite , gypsum , Swartzit and uraninite occur.
In Germany, Schröckingerite has so far only been found in the Johann am Burgfelsen mine and in the Georg am Burgfelsen mine near Wittichen , in Mansfeld and in Saxony in Johanngeorgenstadt , among others . Austrian sites are Radhausberg and Siglitz. The only mining site in Switzerland is the La Creusaz uranium prospect in the canton of Valais.
Schröckingerite is relatively widespread in the USA and has so far been found in several mines in the states of Arizona, Colorado, California, Nevada, New Mexico, New York, Pennsylvania, Texas, Utah and Wyoming.
Other previously known sites for Schröckingerite are in Argentina, France, Italy, Kazakhstan, Namibia, Norway, Poland, Russia, the Czech Republic, Spain, Sweden and the United Kingdom.
Precautions
Due to the toxicity and the strong radioactivity of the mineral, mineral samples from Schröckingerite should only be kept in dust- and radiation-proof 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
literature
- Schröckingerite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 66.3 kB ).
- Schröckingerite - K. Mereiter: Crystal structure and crystallographic properties of a schrockingerite from Joachimsthal, Czech Republic In: Tschermaks Mineralogische und Petrographische Mitteilungen , 1986, 35, 1–18. - American Mineralogist Crystal Structure Database (AMCSD)
Web links
Individual evidence
- ↑ a b Deane K. Smith: An X-ray crystallographic study of schroeckingerite and its dehydration product . In: American Mineralogist , 195, 44, pp. 1020-1025. ( PDF (English), 354 kB ).
- ↑ a b c d e f g h i Mindat - Schröckingerite (English)
- ↑ R. Vochten, L. Van Haverbeke, K. Van Springel: Synthesis of liebigite and andersonite, and study of Their thermal behavior and luminescence . In: The Canadian Mineralogist , 1993, 31, pp. 167-171. ( PDF (English), 633 kB ).
- ↑ Biography of Schröckinger von Neudenberg in: Österreichisches Biographisches Lexikon 1815–1950 1998, 11, p. 228 PDF, 89.7 kB
- ^ Albrecht Schrauf: Schröckingerite, a new mineral from Joachimsthal . In: Tschermaks Mineralogische und Petrographische Mitteilungen , 1873, 1, pp. 137–138. ( PDF, 217 kB ).
- ↑ Webmineral - Schröckingerite (English)
- ↑ M. Bliedtner, M. Martin: Ore and mineral deposits of the central Black Forest. A representation of mining history and mineral deposits. With contributions by Karl-Heinz Huck and Hansjosef Maus , Freiburg i. Br .: geolog. State Office Baden-Württemberg, 1986, p. 560 ff.