Beta fit
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| Beta fit | |
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| General and classification | |
| chemical formula | (Ca, U) 2 (Ti, Nb, Ta) 2 (O, OH) 7 |
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Mineral class (and possibly department) |
Oxides, hydroxides |
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System no. to Strunz and to Dana |
4.DH.15 ( 8th edition : IV / C.16) 02/08/03/01 |
| Crystallographic Data | |
| Crystal system | cubic |
| Crystal class ; symbol | hexakisoctahedral 4 / m 3 2 / m |
| Space group | Fd 3 m |
| Lattice parameters | a = 10.1579 Å |
| Formula units | Z = 10 |
| Frequent crystal faces | (111), (110), (100) |
| Physical Properties | |
| Mohs hardness | 3 to 5.5 |
| Density (g / cm 3 ) | 3.7 to 4.9 |
| Cleavage | no |
| Break ; Tenacity | shell-like to uneven |
| colour | yellow, red, brown, greenish brown, brown to black if metamict |
| Line color | white, greenish gray |
| transparency | translucent to opaque |
| shine | Resin gloss, fat gloss |
| radioactivity | highly radioactive |
| Crystal optics | |
| Refractive index | n = 1.91 to 2.197 |
Betafit (also mendeleevite or blomstrandite ) is a rarely occurring mineral from the mineral class of oxides and hydroxides . It crystallizes in the cubic crystal system with the chemical composition (Ca, U) 2 (Ti, Nb, Ta) 2 (O, OH) 7 and develops mostly octahedral crystals , but also massive mineral aggregates and crusty coatings of initially yellow, red or greenish-brown color, which changes in the course of time due to metamic destruction in solid brown to black.
Special properties
Is Betafit by its uranium content highly radioactive with a specific activity of about 31 k Bq / g (compared to natural potassium 0.0312 kBq / g).
Etymology and history
Betafit was first described in 1912 by Antoine Lacroix . He named the mineral after its type locality Betafo in Madagascar .
classification
In the old systematics of minerals according to Strunz (8th edition) , Betafit still belongs to the division of oxides with the molar ratio metal: oxygen = 2: 3.
After the mineral was redefined on the one hand in its chemical composition and on the other hand the Strunz'sche mineral systematics in the 9th edition was reorganized and more precisely subdivided, the mineral can now be found in the subdivision of "Oxides with the molar ratio metal: oxygen = 1: 2 and comparable with large (± medium-sized) cations; Layers of edge-linked octahedra ”.
The systematics of minerals according to Dana also sorts the Betafit into the class of oxides and hydroxides and there into the subdivision of multiple oxides with Nb, Ta and Ti with the general formula A 2 (B 2 O 6 ) (O, OH, F) . The mineral is named after a subgroup of the pyrochlore group.
Education and Locations
Betafit mainly forms primarily in granitic pegmatites and rarely also in carbonatites . Accompanying minerals include allanite , beryl , biotite , magnetite , microcline , quartz , thorite , titanite and zircon .
Large crystals weighing up to six kilograms can be found at its type locality Betafo in Madagascar. Other localities on this island are Fianarantsoa , Mahajanga and Toliara . So far (as of 2009), Betafit has appeared at the following locations worldwide:
South Australia (Hot Springs area) in Australia; Minas Gerais in Brazil; Jiangxi , Liaoning and Sichuan in China; Kropfmühl (Bavaria) and the Eifel (Rhineland-Palatinate) in Germany; Southern Finland ; Kitaa in Greenland; Barima-Waini in Guyana; Naples , Viterbo , Lombardy and Piedmont in Italy; at Kribi in Cameroon; Bancroft (Ontario) (“Silver Crater Mine” with crystal sizes up to 10 cm) and Québec (Abitibi, Oka) in Canada; at Chitipa in Malawi; Oaxaca in Mexico; Zambezia in Mozambique; Kangwŏn-do in North Korea; Aust-Agder and Telemark in Norway; Silesia in Poland; Eastern Siberia and Murmansk Oblast in Russia; Mintaqah 'Asir in Saudi Arabia; Canton of Graubünden in Switzerland; near Banská Bystrica in Slovakia; South Africa ; Alai in Tajikistan; Bohemia and Moravia in the Czech Republic; as well as in different regions of the USA .
Mineral samples from Betafit were also brought back to the Mare Crisium on the moon during the Luna mission 24 .
Crystal structure
Betafit crystallizes in the cubic crystal system in the space group with the lattice parameter a = 10.1579 Å and 10 formula units per unit cell .
See also
Individual evidence
- ↑ a b c d Webmineral - Betafite (English)
- ↑ a b American Mineralogist Crystal Structure Database - Betafite (English, 1989)
- ↑ a b Betafite at mindat.org (engl.)
- ↑ Entry at dic.academic.ru
- ↑ IMA / CNMNC List of Mineralnames (English, PDF 1.8 MB, p. 31)
- ↑ Mindat - Localities for Betafite
- ↑ American Mineralogist Crystal Structure Database - Betafite (English, 1989)
literature
- Petr Korbel, Milan Novák: Encyclopedia of Minerals . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 87 .
Web links
- Mineral Atlas: Betafit (Wiki)
- Mineral data sheet - Betafite (English, PDF 70.9 kB)