Baotite

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Baotite
Baotite-661893.jpg
General and classification
chemical formula Ba 4 Ti 4 (Ti, Nb, Fe) 4 [Cl | O 16 | Si 4 O 12 ]
Mineral class
(and possibly department) 		Silicates and Germanates
System no. to Strunz
and to Dana 		9.CE.15 ( 8th edition : VIII / E.08)
60.01.02.01
Crystallographic Data
Crystal system tetragonal
Crystal class ; symbol tetragonal-dipyramidal; 4 / m
Space group I 4 1 / a (No. 88)Template: room group / 88
Lattice parameters a  = 19.99  Å ; c  = 5.908 Å
Formula units Z  = 4
Physical Properties
Mohs hardness 6th
Density (g / cm 3 ) 4.42 to 4.72; on average 4.57
Cleavage good on {110}
Break ; Tenacity splintery
colour light yellow, light brown, black
Line color White
transparency transparent to translucent
shine Glass gloss
Crystal optics
Refractive indices n ω  = 2.16
n ε  = 1.94
Birefringence δ = 0.220
Optical character uniaxial positive

Baotit ( Chinese  包头矿 , Pinyin Baotoukuang ) is a rare mineral in the mineral class of silicates and germanates . It crystallizes in the tetragonal crystal system with the chemical composition Ba 4 Ti 4 (Ti, Nb, Fe) 4 [Cl | O 16 | Si 4 O 12 ]. It mainly develops light yellow or light brown to black crystals of up to ten centimeters in size.

Etymology and history

Peng Qirui 彭琪瑞 (1917–1985 ) first published about baotite in 1959 in the scientific journal Scientia Geologica Sinica ( Dizhi kexue ). The mineral was discovered in the Bayan Obo Mine , located in the Shiguai (Xiguit) district of the prefecture-level city of Baotou in Inner Mongolia , People's Republic of China . VI Semonov also described the new mineral. The naming "Baotit" was introduced as a transcription of Semonov's name, the original name in the Chinese first description was (in the transcription) "Pao-t'ou-k'uang". This results from the different names in Russian and Chinese for the type locality after which the mineral is named. Simonov's analysis revealed the chemical composition Ba 4 Ti 7 NbO 16 (SiO 3 ) 4 Cl. E. Wm. Heinrich, Wm. H. Boyer and FA Crowley also later described Baotit that they found a second site in Montana .

classification

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the baotite belonged to the mineral class of "silicates and germanates" and there to the department of " ring silicates ", where together with bario-orthojoaquinite , byelorussite- (Ce) , Cerchiarait , Joaquinit- (Ce) , Nagashimalith , Orthojoaquinit- (Ce) , Orthojoaquinit- (La) , Strontiojoaquinit , Strontio-Orthojoaquinit , Taramellit , Titantaramellit and Verplanckit the "Joaquinite group" / formed with the system number VIII E.08.

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 baotite in the "ring silicates" section. However, this is now further subdivided according to the chemical structure, so that the mineral can be found according to its composition in the subdivision "[Si4O12] 8− four-single rings without island-like, complex anions", where it now contains the unnamed group with the system number VIII.CE.15 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns baotite to the class of "silicates and germanates" and there in the department of "ring silicates: four rings" in the sub-group "ring silicates: four rings as titanosilicates". Here it is in the unnamed group with the system no. 04/02/07 to find.

Crystal structure

Baotite crystallizes in the tetragonal crystal system in the space group I 4 1 / a (space group no. 88) with the lattice parameters a  = 19.99  Å and c = 5.908 Å as well as 4 formula units per unit cell . Template: room group / 88

properties

The mineral is optically uniaxial with the refractive indices n ω = 2.16 and n ε = 1.94; the birefringence δ is 0.220. It is strongly pleochroic between colorless and light greenish yellow.

Education and Locations

In Bayan Obo, the mineral occurs in Proterozoic rocks in quartz veins together with galena and pyrite . The quartz veins go back to the intrusion of Variscan alkali granites and syenites .

A total of 20 sites of baotite are known.

Besides the type locality in Bayan Obo (Inner Mongolia), no other sites are known in China.

No sites are known from Germany, Austria and Switzerland. In Europe, however, there are other sites: in the Czech Republic in the Bohemian-Moravian Highlands (Vysočina), in Norway in Troms , in the United Kingdom in Scotland and also in the Ukraine in the Donetsk region .

There are other sites in Canada (a site in Ontario ), in the Dem. Rep. Congo in Kivu , in Kyrgyzstan , in New Zealand , Pakistan , Russia and Tajikistan . There are also localities in the USA , in California and Montana.

See also

literature

  • Michael Fleischer , ECTChao: New minerals. Pao-t'ou-k'uang. In: American Mineralogist , Vol. 45, 1960, pp. 753–756, Baotit from p. 754 ( PDF , 292 kB)
  • Michael Fleischer: New minerals. Baotite (= Pao-t'ou-k'uang) In: American Mineralogist , Vol. 46, 1961, pp. 464–468, Baotite from p. 466 ( PDF , 280 kB)
  • E. Wm. Heinrich, Wm. H. Boyer, FA Crowler: Baotite (Pa-t'ou-k'uang) from ravalli country, montana In: American Mineralogist , Vol. 47, 1963, pp. 464-468 ​​( PDF )

Web links

Commons : Baotite  - collection of images, videos and audio files

Individual evidence

  1. ↑ a b c d YV Nekrasov, VI Ponomarev, VI Simonov, DM Kheiker: Refinement of the atomic structure of baotite and the isomorphic relationships in this mineral. In: Soviet Physics - Crystallography Volume 14 (1969), pp. 508-514 ( PDF 548.3 kB )
  2. ↑ a b Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties . 5th completely revised and supplemented edition. Weise, Munich 2008, ISBN 978-3-921656-70-9 .
  3. ↑ Mindat - Baotite
  4. ↑ Malcom E. Back: Fleischer's Glossary of Mineral Species . 11th edition. Mineralogical Record, Tucson, Arizona (AZ) 2014, p. 20 .
  5. ↑ a b Baotite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 59.7 kB )
  6. ^ E. Wm. Heinrich, Wm. H. Boyer, FA Crowler: Baotite (Pa-t'ou-k'uang) from ravalli country, montana In: American Mineralogist , Volume 47, 1963, pp. 464-468 ​​( PDF )
  7. ↑ Mindat - Number of localities for baotite
  8. ↑ a b List of locations for baotite in the Mineralienatlas and Mindat