Hibonite
| Hibonite | |
|---|---|
 |
|
| General and classification | |
| chemical formula | (Ca, Ce) (Mg, Fe 2+ ) Al 10 (Ti 4+ , Al) O 19 |
|
Mineral class (and possibly department) |
Oxides and hydroxides |
|
System no. to Strunz and to Dana |
4.CC.45 ( 8th edition : IV / C.08) 04/07/01/01 |
| Crystallographic Data | |
| Crystal system | hexagonal |
| Crystal class ; symbol | dihexagonal-dipyramidal; 6 / m 2 / m 2 / m |
| Room group (no.) | P 6 3 / mmc (No. 194) |
| Lattice parameters | a = 5.613 Å ; c = 22.285 Å |
| Formula units | Z = 2 |
| Physical Properties | |
| Mohs hardness | 7.5 to 8 |
| Density (g / cm 3 ) | measured: 3.84; calculated: 4.09 |
| Cleavage | good after {0001} |
| colour | brown, black, red-brown |
| Line color | brown |
| transparency | translucent to opaque |
| shine | Metal luster, glass luster |
| radioactivity | weakly radioactive |
| Crystal optics | |
| Refractive indices |
n ω = 1.807 n ε = 1.79 |
| Optical character | uniaxial negative |
| Pleochroism | gray-gray-brown |
Hibonite is a rarely occurring mineral from the mineral class of " oxides and hydroxides ". It crystallizes in the hexagonal crystal system with the general chemical composition ( Ca , Ce ) ( Al , Ti , Mg ) 12 O 19 . The elements indicated in brackets can represent each other, but are always in the same proportion to the other components of the mineral.
Hibonite mostly develops tabular, more rarely also prismatic crystals in the colors brown, black and red-brown. Its Mohs hardness is 7.5 to 8 and its measured density is 3.84 g / cm³.
Etymology and history
Hibonite was first discovered in 1956 in the eluvial deposit of Esiva near Maromby, in the Amboasary district , Anosy region (Fort Dauphin) in the Toliara province in Madagascar and described by Curien, Guillemin, Orcel and Sternberg. It was named after its discoverer Paul Hibon .
classification
In the now outdated system of minerals according to Strunz (8th edition) , the hibonite still belongs to the general division of "Oxides with a molar ratio of metal: oxygen = 2: 3".
With the revision of Strunz's mineral systematics in the 9th edition , the class of oxides (and hydroxides) was partially re-classified and more precisely divided according to the size of the cations involved in the compound . Due to its chemical composition, the mineral is therefore in the department of “Oxides with the molar ratio of metal: oxygen = 2: 3, 3: 5 and comparable” and there in the subdivision “With large and medium-sized cations”, where it is together with Batiferrite , Barioferrit , Diaoyudaoit , Haggertyit , Hawthorneit , Lindqvistit , magnetoplumbite , Nezilovit , Plumboferrit , Yimengit the unnamed group 4.CC.45 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , also sorts the hibonite into the class of oxides, but there into the division of " multiple oxides with O 19 groups ", where together with Yimengit and Hawthorneit it is the hexagonal in space group P. 6 3 / mmc crystallizing group 04/07/01 forms.
Crystal structure
Hibonite crystallizes hexagonally in the space group P 6 3 / mmc (space group no. 194) with the lattice parameters a = 5.613 Å and c = 22.285 Å as well as two formula units per unit cell .
properties
Like many rare earth minerals, hibonite also contains traces of uranium and thorium . For this reason it is classified as weakly radioactive . It has a specific activity of around 88.2 Bq / g (for comparison: natural potassium 31.2 Bq / g).
Education and Locations
Hibonite forms metamorphically in granulite , gneiss , limestone or pyroxenite . Calcium- and aluminum-rich hibonite inclusions also occur as a presolar mineral in primitive meteorites .
Hibonite has so far been found at 23 sites around the world , including the Tanezrouft desert of the Algerian Sahara ; at Charleroi in Belgium; at Xingtai in China; in Israel's Negev desert ; in the Efremovka meteorite in Kazakhstan ; on Tagish Lake in Canada and Madagascar ; in the province of Chihuahua in Mexico; in the “Søve Mine” in the Norwegian province of Telemark ; in the Far Eastern and West Siberian regions of Russia ; on the Krymka meteorite in Ukraine ; Kentucky and Utah in the USA and in southern Yemen .
See also
literature
- Paul Ramdohr , Hugo Strunz : Klockmann's textbook of mineralogy . 16th edition. Ferdinand Enke Verlag, 1978, ISBN 3-432-82986-8 , pp. 518 .
Web links
- Mineral Atlas: Hibonite (Wiki)
Individual evidence
- ↑ a b c d Webmineral - Hibonite (English).
- ↑ a b c American Mineralogist Crystal Structure Database - Hibonite (English, 1996).
- ↑ a b Hibonite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 70 kB ).
- ↑ IMA / CNMNC List of Mineral Names - Hibonite (English, PDF 1.8 MB; p. 120).
- ↑ Find location list for hibonite in the Mineralienatlas and Mindat .