Čejkait
| Čejkait | |
|---|---|
 |
|
| General and classification | |
| chemical formula | Na 4 [UO 2 | (CO 3 ) 3 ] |
|
Mineral class (and possibly department) |
Carbonates and nitrates (formerly carbonates, nitrates and borates) |
|
System no. to Strunz and to Dana |
5.ED.50 ( 8th edition : V / F.02) 01/14/07/01 |
| Crystallographic Data | |
| Crystal system | triclinic |
| Crystal class ; symbol | triclinic-pedial or -pinacoidal |
| Room group (no.) | P 1 or P 1 (No. 1 or 2) |
| Lattice parameters |
a = 9.291 (2) Å ; b = 9.292 (2) Å; c = 12.895 (2) Å α = 90.73 (2) °; β = 90.82 (2) °; γ = 120.00 (1) ° |
| Formula units | Z = 4 |
| Physical Properties | |
| Mohs hardness | not definable |
| Density (g / cm 3 ) | measured: 3.67 (1); calculated: 3,766 (5) |
| Cleavage | Please complete |
| Break ; Tenacity | shell-like to uneven |
| colour | light yellow |
| Line color | light yellow |
| transparency | opaque |
| shine | Glass gloss |
Čejkait is a very rarely occurring mineral from the mineral class of " carbonates and nitrates " (formerly carbonates, nitrates and borates ). It crystallizes in the triclinic crystal system with the composition Na 4 [UO 2 | (CO 3 ) 3 ], so it is chemically seen a the uranyl scoring sodium - uranyl carbonate .
Čejkait only develops microscopic crystals between 0.2 and 0.6 micrometers in diameter with an indistinct, hexagonal habit . It is usually found in the form of thin, crusty coatings and efflorescence or as tiny, spherical aggregates . The color and color of the streak of the mineral are light yellow.
Etymology and history
Čejkait was first discovered in the Einigkeit mine near Jáchymov (German Sankt Joachimsthal ) in the Czech Republic and described in 2003 by Petr Ondruš, Roman Skála, Františsek Veselovský, Jiří Sejkora and Cecilia Vitti, who named the mineral after Jiří Čejka , for its outstanding contributions to crystal chemistry of uranium minerals to honor.
classification
In the meantime outdated, but still in use 8th edition of the mineral classification by Strunz of Čejkait even for common class of "carbonates, nitrates and borates" and then to the Department of "uranyl carbonate" where he and belonged Andersonit , Bayleyit , Fontanit , Grimselit , Liebigit , Metazellerit , Swartzit and Zellerit formed the unnamed group V / F.02 .
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 the Čejkait to the newly defined class of "carbonates and nitrates" (the borates form a separate class here), but also in there the department of "uranyl carbonates". However, this is further subdivided according to the molar ratio of uranium dioxide (UO 2 ) to the carbonate complex (CO 3 ), so that the mineral can be found in the sub-section "UO 2 : CO 3 = 1: 4", where it is based on its composition forms the unnamed group 5.ED.50 as the only member .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Čejkait, like the outdated Strunzian system, to the common 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 01/14/07 within the subdivision of " Anhydrous carbonates with simple formula A + CO 3 ".
Crystal structure
Čejkait crystallizes triclinically in the space group P 1 or P 1 (space group no. 1 or 2) with the lattice parameters a = 9.291 (2) Å ; b = 9.292 (2) Å; c = 12,895 (2) Å; α = 90.73 (2) °; β = 90.82 (2) ° and γ = 120.00 (1) ° as well as 4 formula units per unit cell .
properties
The mineral is classified as very radioactive due to its uranium content of up to 44.9% and has a specific activity of around 80.325 k Bq / g (for comparison: natural potassium 31.2 Bq / g).
Education and Locations
Čejkait formed secondarily on calcite - veins , where it mostly in paragenesis with uraninite , Andersonit and schröckingerite be found.
Apart from its type locality Jáchymov, the mineral has so far only appeared in Rožná in the Czech Republic . Other sites known so far (as of 2012) are Kővágószőlős in the Hungarian Mecsek Mountains , the "Eureka" pit near Torre de Cabdella in the Spanish municipality of Pallars Jussà and the "Apex" pit on the Reese River in Lander County (Nevada) in the USA.
Precautions
Due to the toxicity and the strong radioactivity of the mineral, mineral samples from Čejkait should only be kept in dust-tight 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 face masks and gloves should be worn when handling the mineral.
See also
literature
- Petr Ondruš, Roman Skála, Františsek Veselovský, Jiří Sejkora, Cecilia Vitti: Čejkaite, the triclinic polymorph of Na 4 (UO 2 ) (CO 3 ) 3 - a new mineral from Jáchymov, Czech Republic . In: American Mineralogist . tape 88 , no. 4 , 2003, p. 686–693 , doi : 10.2138 / am-2003-0422 ( short description from American Mineralogist online - accessed via De Gruyter Online).
Web links
- Mineral Atlas: Čejkait (Wiki)