Bromellite
| Bromellite | |
|---|---|
 |
|
| General and classification | |
| other names | |
| chemical formula | BeO |
|
Mineral class (and possibly department) |
Oxides and hydroxides |
|
System no. to Strunz and to Dana |
4.AB.20 ( 8th edition : IV / A.03) 02/04/02/02 |
| Crystallographic Data | |
| Crystal system | hexagonal |
| Crystal class ; symbol | dihexagonal-pyramidal; 6 mm |
| Space group | P 6 3 mc (No. 186) |
| Lattice parameters | a = 2.70 Å ; c = 4.38 Å |
| Formula units | Z = 2 |
| Physical Properties | |
| Mohs hardness | 9 |
| Density (g / cm 3 ) | measured: 3.017; calculated: 3.044 |
| Cleavage | clearly after {10 1 0} |
| colour | colorless, white to creamy white, pale yellow |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass gloss |
| Crystal optics | |
| Refractive indices |
n ω = 1.705 to 1.719 n ε = 1.733 |
| Birefringence | δ = 0.028 |
| Optical character | uniaxial positive |
| Other properties | |
| Special features | Pyroelectric, yellowish white fluorescence , highly toxic |
Bromellite is a very rarely occurring mineral from the mineral class of " oxides and hydroxides " with the chemical composition BeO and is therefore chemically beryllium oxide .
Bromellite is transparent to translucent and crystallizes in the hexagonal crystal system , but usually only develops small, colorless or white to creamy white, occasionally pale yellow crystals in the millimeter range with a glass-like sheen on the surfaces. However, crystal sizes of up to 10 centimeters are also known.
With a Mohs hardness of 9, bromellite is one of the hard minerals that, like the reference mineral corundum, can only be scratched by diamond- hard materials.
Etymology and history
Bromellite was first found in the Swedish mining community Långban and described in 1925 by Gregori Aminoff , who named the mineral in honor of the Swedish doctor and mineralogist Magnus von Bromell (1679–1731) after him.
Type material of the mineral is kept in the Naturhistoriska riksmuseet in Stockholm (Sweden).
classification
Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the bromellite belonged to the mineral class of "oxides and hydroxides" and there to the department of "oxides with the molar ratio metal: oxygen = 1: 1 and 2: 1 (M 2 O, MO) ", where he named the" bromellite series "with the system no. IV / A.03 and the other member zincite .
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 classifies the bromellite in the division of "Metal: Oxygen = 2: 1 and 1: 1". However, this is further subdivided according to the exact molar ratio and, if necessary, the relative size of the cations involved, so that the mineral is classified according to its composition in the subsection “Cation: Anion (M: O) = 1: 1 (and up to 1: 1.25 ); with only small to medium-sized cations "can be found, where together with zincite the" zincite group "with the system no. 4.AB.20 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the bromellite to the class of "oxides and hydroxides" and there in the "oxides" category. Here it can also be found together with zincite in the unnamed group 04.02.02 within the subsection “ Simple oxides with a cation charge of 2+ (AO) ”.
Chemism
In its pure form, bromellite consists of 36.03% beryllium and 63.97% oxygen and thus has the highest beryllium concentration of all known minerals. However , calcium , barium and magnesium were already observed as foreign additions in the first analysis by GK Almström . The small admixtures of Sb 2 O 5 and Al 2 O 3 that were also found , on the other hand, are more likely due to contamination of the samples with the mineral Swedenborgite , according to Almström .
Crystal structure
Bromellite crystallizes isotypically with zincite in the hexagonal crystal system in the space group P 6 3 mc (space group no. 186) with the lattice parameters a = 2.70 Å and c = 4.38 Å as well as two formula units per unit cell .
properties
morphology
The bromellite crystals are usually well developed and have a prismatic habit , stretched towards [0001] and a one-sided (hemimorphic) pyramidal closure. Tabular crystals parallel {0001} and rosette-shaped mineral aggregates are also possible.
Physical Properties
Bromellite is pyroelectric , which means that it charges electrically when the temperature changes at intervals. When exposed to long-wave or short-wave UV light , yellowish-white fluorescence appears .
Education and Locations
Bromellite is formed by hydrothermal processes in calcite veins, in hematite - skarns and scarified limestone , in natrolite - drusen , hydrothermally formed nepheline , and in syenite - pegmatites . Accompanying minerals include chamosite , diaspore , manganophyllite , natrolite, Richterite and Swedenborgite .
So far, the mineral has only been found at nine locations worldwide (as of 2009): In the "Bollingers Mine" near Torrington (New South Wales) in Australia; at the Xianghualing Mine in Linwu County, Hunan Province, China; in the “Costabonne” mine near Prats-de-Mollo-la-Preste in France; near Sagåsen in the Norwegian province of Telemark ; Pitkyaranta , Kola and Yekaterinburg in Russia; as well as at its type locality Långban and at Pajsberg in Sweden.
use
Bromellite is a good conductor of heat and is used, among other things, in thermocouple protective tubes, melting crucibles , spark plugs and in electronics as a heat sink for semiconductor components and in reactor technology.
Bromellite is one of the rare collector minerals, but is occasionally also available in a polished form.
Precautions
As a highly toxic compound, bromellite should only be kept in dust-tight containers. The mineral is classified as damaging to the skin and lungs, so absorption into the body, especially via the respiratory tract ( inhalation ), should be prevented in any case and, to be on the safe side, direct body contact should be avoided and face mask and gloves worn when handling the mineral.
See also
literature
- G. Aminoff: About beryllium oxide as a mineral and its crystal structure . In: Journal of Crystallography . tape 62 , 1925, pp. 113–122 ( rruff.info [PDF; 1.9 MB ; accessed on November 22, 2017]).
- Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 499 (first edition: 1891).
Web links
- Mineral Atlas: Bromellite (Wiki)
- RRUFF Database-of-Raman-spectroscopy - Bromellite (English)
- American Mineralogist Crystal Structure Database - Bromellite (English)
Individual evidence
- ↑ a b c d Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 184 .
- ↑ a b Webmineral - Bromellite (English)
- ↑ a b c d Bromellite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 60 kB ]).
- ↑ a b c Mindat - Bromellite (English)
- ↑ a b G. Aminoff: About beryllium oxide as a mineral and its crystal structure . In: Riksmuseets mineralogiska avdelning . Stockholm March 1925, p. 113–122 ( rruff.info [PDF; 1 kB ; accessed on October 18, 2007]).
- ↑ Naturhistoriska riksmuseet - Type specimens, Holotypes and some important cotypes (English)
- ↑ Webmineral - Mineral Species sorted by the element Be (Beryllium)
- ↑ Find location list for bromellite in the Mineralienatlas and Mindat
- ↑ List of rare collector minerals on diamant-boerse.com from July 25, 2008 (accessed: November 22, 2017)
- ↑ Sinhalite.org - bromellite (with examples of pictures of polished bromellites)
- ↑ Entry for CAS no. 1304-56-9 in the GESTIS substance database of the IFA , accessed on March 13, 2011(JavaScript required) .