Bütschliit
| Bütschliit | |
|---|---|
| General and classification | |
| other names |
Buetschliit |
| chemical formula | K 2 Ca [CO 3 ] 2 |
|
Mineral class (and possibly department) |
Carbonates and nitrates (formerly carbonates, nitrates and borates) |
|
System no. to Strunz and to Dana |
5.AC.15 ( 8th edition : V / B.05) 03/14/01/01 |
| Crystallographic Data | |
| Crystal system | trigonal |
| Crystal class ; symbol | ditrigonal-scalenohedral; 3 2 / m |
| Room group (no.) | R 3 m (No. 166) |
| Lattice parameters | a = 5.38 Å ; c = 18.16 Å |
| Formula units | Z = 3 |
| Physical Properties | |
| Mohs hardness | not defined |
| Density (g / cm 3 ) | calculated: 2.607 |
| Cleavage | Please complete |
| colour | gray-yellow, brownish-gray, light green |
| Line color | not defined |
| transparency | translucent |
| shine | Please complete |
| Crystal optics | |
| Refractive indices |
n ω = 1.595 n ε = 1.455 |
| Birefringence | δ = 0.140 |
| Optical character | uniaxial negative |
Bütschliit is a very 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 composition K 2 Ca [CO 3 ] 2 , so from a chemical point of view it is a potassium - calcium carbonate belonging to the double salts .
Bütschliit is translucent and has so far only been found in the form of microscopic, barrel-shaped crystals of gray-yellow or brownish-gray color. Light green colors are also possible due to foreign admixtures .
Etymology and history
Bütschliit was first discovered in the Grand Canyon National Park of Arizona and near Coolin in Bonner County (Idaho) in the United States. The mineral was described in 1947 by Charles Milton and Joseph M. Axelrod, who named it after Johann Adam Otto Bütschli (1848–1920). This was professor of zoology at the University of Heidelberg and studied the potassium and calcium salts.
Type material of the mineral has been deposited in the National Museum of Natural History , Washington, DC (Register No. 105675, 105676).
classification
In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , Bütschliit belonged to the common mineral class of "carbonates, nitrates and borates" and there to the department of "anhydrous carbonates without foreign anions ", where it together with Eitelite , Fairchildite , Gregoryite , Juangodoyit , Nyerereit , Shortit and Zemkorit formed the unnamed group V / B.05 .
The 9th edition of Strunz's mineral systematics , which has been in force since 2001 and is used by the International Mineralogical Association (IMA), assigns the Bütschliit to the class of "carbonates and nitrates" (the borates form a separate class here) and also to the department of “Carbonates without additional anions; without H 2 O “. However, this section is further subdivided according to the element group belonging to the cations , so that the mineral can be found according to its composition in the sub-section " Alkali and alkaline earth carbonates", where it is the only member of the unnamed group 5.AC.15 .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Bütschliit, like the old Strunz system, to the class of "carbonates, nitrates and borates" and there to the department of "anhydrous carbonates". Here he is to be found as the only member of the unnamed group 14.03.01 within the subdivision of " Anhydrous carbonates with a compound formula A 2+ B 2+ (CO 3 ) 2 ".
Modifications and varieties
The compound K 2 Ca (CO 3 ) 2 is dimorphic and, in addition to the trigonal crystallizing Bütschliite, also occurs as a hexagonal high-temperature modification fairchildite. The transition temperature is 820 Kelvin (about 547 ° C).
Education and Locations
Bütschliit forms in slag from melted wood ash from partially burned trees, mainly hemlock and other firs . In addition to fairchildite, calcite can also occur as accompanying minerals .
Apart from its type localities Grand Canyon National Park and Coolin, Bütschliit could so far (as of 2012) only be detected at Long Shop in Montgomery County (Virginia) .
Crystal structure
Bütschliit crystallizes trigonal in the space group R 3 m (space group no. 166) with the lattice parameters a = 5.38 Å and c = 18.16 Å as well as 3 formula units per unit cell .
See also
literature
- Alexandra Navrotsky, Robert L. Putnam, Camilla Winbo, Erik Rosén: Thermochemistry of double carbonates in the K 2 CO 3 –CaCO 3 system , in: American Mineralogist , Volume 82 (1997), pp. 546-548 ( PDF 49.1 kB )
Web links
Individual evidence
- ↑ a b c d e 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. 290 .
- ↑ a b c John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols: Bütschliite , in: Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 63.5 kB )
- ↑ a b c Mindat - Bütschliite