Bøgvadit
| Bøgvadit | |
|---|---|
| General and classification | |
| other names |
|
| chemical formula | Ba 2 SrNa 2 [Al 4 F 20 ] |
|
Mineral class (and possibly department) |
Halides |
|
System no. to Strunz and to Dana |
3.CF.15 ( 8th edition : III / B.03) 06/11/20/01 |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-dipyramidal; 2 / m 2 / m 2 / m or orthorhombic-pyramidal; mm 2 |
| Space group | Pnmn (No. 58, position 5) or Pn 2 n (No. 34, position 3) |
| Lattice parameters | a = 7.11 Å ; b = 19.91 Å; c = 5.35 Å |
| Formula units | Z = 2 |
| Frequent crystal faces | {110}, {010}, {012} |
| Physical Properties | |
| Mohs hardness | > 3 |
| Density (g / cm 3 ) | measured: 3.85; calculated: 3.898 |
| Cleavage | Please complete |
| Break ; Tenacity | uneven |
| colour | colorless |
| Line color | White |
| transparency | transparent |
| shine | Glass gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.433 n β = 1.436 n γ = 1.439 |
| Birefringence | δ = 0.006 |
| Optical character | biaxial negative |
| Axis angle | 2V = 87 ° (measured); 85 ° (calculated) |
Bøgvadit is a very rarely occurring mineral from the mineral class of " halides ". It crystallizes in the orthorhombic crystal system with the chemical composition Ba 2 SrNa 2 [Al 4 F 20 ] and thus structurally belongs to the framework-forming aluminofluorides ( tecto-aluminofluorides ) with barium , strontium and sodium .
Bøgvadit is colorless and transparent and mostly develops blocky, parallel to the a-axis stretched crystals up to about 0.15 millimeters in size. The crystal faces are often rounded and corroded.
Etymology and history
Was first discovered Bøgvadit in cryolite - deposit at Ivittuut in southwest Greenland . It was scientifically described in 1988 by Hans Pauly and Ole V. Petersen, who named the mineral after Richard Bøgvad (1897–1952) after the former chief geologist of the Øresund A / S mining company .
classification
Already in the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the Bøgvadite belonged to the mineral class of the "halides" and there to the division of the "anhydrous double halides", where it together with calcjarlite , colquiriite , elpasolite , jarlite , jørgensenite , cryolite , Cryolite ionite and simmonsite the "cryolite-elpasolite group" with system no. III / B.03 formed.
The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also assigns Bøgvadit to the “halides” class, but in the “complex halides” department. This is also further subdivided according to the crystal structure, so that the mineral can be found in the sub-section “Framework-Aluminofluoride ( Tecto-Aluminofluoride )” according to its structure , where it is the only member of the unnamed group 3.CF.15 .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Bøgvadit to the class of "halides" and there in the section "Complex halides - aluminum fluorides". Here he is the only member of the unnamed group 11.06.20 within the sub-section “Complex halides - aluminum fluorides with different formulas”.
Crystal structure
Bøgvadit crystallizes orthorhombically in the space group Pnmn (space group no. 58, position 5) or space group Pn 2 n (space group no. 34, position 3) with the lattice parameters a = 7.11 Å ; b = 19.91 Å and c = 5.35 Å and 2 formula units per unit cell .
Education and Locations
Bøgvadit forms in cryolite - deposits . Baryte , jarlite , potassium mica , quartz and ralstonite appear as accompanying minerals .
Apart from the type locality Ivittuut in Greenland, no other location for Bøggildit is known so far (as of 2016).
See also
literature
- Hans Pauly, Ole V. Petersen: Bøgvadite, Na 2 SrBa 2 Al 4 F 2 0, a new fluoride from the cryolite deposit, Ivigtut, S. Greenland , in: Bulletin of the Geological Society of Denmark , Copenhagen 1988 ( PDF 1, 17 MB )
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. 166 .
- ↑ a b c Bøgvadite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 69.5 kB )
- ↑ a b c d e Mindat - Bøgvadite
- ↑ Find location list for Bøgvadit at the Mineralienatlas and at Mindat