Sogdianite
| Sogdianite | |
|---|---|
| General and classification | |
| chemical formula | K Zr 4+ 2 Li 3 Si 12 O 30 |
|
Mineral class (and possibly department) |
Silicates and germanates - ring silicates |
|
System no. to Strunz and to Dana |
9.CM.05 ( 8th edition : VIII / E.22) 63.02.01a.13 |
| Similar minerals | Sugilite |
| Crystallographic Data | |
| Crystal system | hexagonal |
| Crystal class ; symbol | dihexagonal-dipyramidal; 6 / m 2 / m 2 / m |
| Space group | P 6 / mcc (No. 192) |
| Lattice parameters | a = 10.1240 Å ; c = 14.3198 Å |
| Formula units | Z = 2 |
| Physical Properties | |
| Mohs hardness | 7th |
| Density (g / cm 3 ) | 2.9 |
| Cleavage | completely after (0001) |
| colour | purple, light purple |
| Line color | Please complete |
| transparency | transparent |
| shine | Glass gloss |
| radioactivity | hardly measurable |
| Crystal optics | |
| Refractive indices |
n ω = 1.608 n ε = 1.606 |
| Birefringence | δ = 0.002 |
| Optical character | uniaxial negative, uniaxial positive |
| Other properties | |
| Special features | Fluorescence: LW: dark purple, KW: dark red |
The mineral Sogdianite is a rarely occurring ring silicate from the milarite group and has the chemical composition K Zr 4+ 2 Li 3 Si 12 O 30 . It crystallizes in the hexagonal crystal system and develops violet crystals , comparable in color to Kunzite .
Etymology and history
Sogdianit was discovered in the moraines of the Darai-Pioz- glacier in Alay Mountains in Tajikistan described and 1968 by VD Dusmatov, AF Efimov, ZT Kataeva, LA Khoroshilova and KP Yanulov as a new mineral of Milaritgruppe. They named the mineral after the ancient name of the place where it was found, the Empire of Sogdia in Central Asia , now Tajikistan.
classification
In the outdated, but partly still in use, 8th edition of the mineral classification according to Strunz , the Sogdianite belongs to the general division of " Ring Silicates (Cyclosilicates)", where it is used together with Almarudit , Armenit , Berezanskit , Brannockit , Chayesit , Darapiosit , Dusmatovit , Eifelit , Emeleusit , Faizievit , Merrihueit , Oftedalit , Osumilith , Osumilith- (Mg) , Poudretteit , Roedderite , Shibkovite , Sugilite , Trattnerite and Yagiit the " Milarit-Osumilith-Gruppe " with the system no. VIII / E.22 forms.
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 Sogdianite in the “ring silicates” section. This is, however, further subdivided according to the structure of the rings, so that the mineral can be found in the sub-section "[Si 6 O 18 ] 12− -six double rings" according to its structure . With Almarudit, Armenit, Berezanskit, Brannockit, Chayesit, Darapiosit, Dusmatovit, Eifelit, Friedrichbeckeit , Klöchit , Merrihueit, Milarit, Oftedalit, Osumilith, Osumilith- (Mg), Poudretteit, Roedderit, Shibkovitit, Roedderit, Shibkovite, Sugilite, Roedderite " Milaritgruppe " with the system no. 9.CM.05 .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Sogdianite to the class of "silicates and germanates", but there in the more finely divided division of "ring silicates: condensed rings". Here it is in the " Milarite Osumilith Group (Milarite Osumilith Subgroup) " with the system no. 63.02.01a can be found in the subsection “ Ring Silicates : Condensed, 6-membered Rings”.
Chemism
Sogdianite with an almost ideal end link composition is only known from the type locality in Tajikistan. Otherwise it forms complex mixed crystals with sugilite (Na and Fe 3+ contents), Berezansite (Ti 4+ contents), Brannockite (Sn 4+ ) and darapiosit (Na and Mn 2+ contents).
The complete Sogdianite-Sugilite mixed crystal series of the Darai-Pioz Glacier is documented and the other compositions that can be found in the literature are mixed crystals, e.g. B. of Sogdianite, Sugilite, Berezanskit and Sugilith-Al (hypothetical end member).
Crystal structure
Sogdianite crystallizes hexagonally in the space group P 6 / mcc (space group no. 192) with the lattice parameters a = 10.1240 Å and c = 14.3198 Å as well as two formula units per unit cell .
Sogdianite is isotypic to milarite , which means that it crystallizes with the same structure as milarite. The 12-fold coordinated C position is fully occupied with potassium (K + ), whereas the 9-fold coordinated B position is unoccupied. Zirconium Zr 4+ is only incorporated on the 6-fold coordinated A position, lithium (Li + ) on the tetrahedrally coordinated T2 position. The T1 position, which builds up the 6 double rings, only contains silicon (Si 4+ ).
Education and Locations
Sogdianite forms in pegmatite veins and alkaline granites .
The type locality is the Darai-Pioz- glacier in Alay Mountains in Tajikistan , where in rocks pegmatitic origin in the moraines is found. Sogdianite occurs here together with quartz , microcline , aegirine and rare earth minerals such as thorite and stillwellite .
In addition, Mindat only lists 2 other locations:
- The Golden Horn batholith of Okanogan County (Washington) in the United States and the
- Wessels Mine (Wessel's Mine) in the Kalahari Manganese Field, North Cape (Province) , South Africa .
At the Golden Horn Batholith, Sogdianite occurs together with aegirine , bastnasite - (Ce), gadolinite - (Y), titanite , zektzerite and arfvedsonite .
See also
literature
- Paul Ramdohr , Hugo Strunz : Klockmann's textbook of mineralogy . 16th edition. Ferdinand Enke Verlag, 1978, ISBN 3-432-82986-8 , pp. 714 .
- Stefan Weiß: The large Lapis mineral directory . 5th edition. Christian Weise Verlag, Munich 2008, ISBN 3-921656-17-6 .
Web links
- Mineral Atlas: Sogdianite (Wiki)
- Mineral data sheet - Sogdianite (PDF; 67 kB)
Individual evidence
- ↑ a b c d e f EV Sokolova, FC Hawthorne, LA Pautov (2000): The Crystal Chemistry Of Li-bearing Minerals With The Milarite-Type Structure: The Crystal Structure Of End-Member Sogdianite , In: The Canadian Mineralogiste , 38 , Pp. 853–859 ( PDF, 698 kB )
- ↑ a b Webmineral - Sogdianite
- ↑ a b c d e f g h i j k VD Dusmatov, AF Efimov, ZT Kataeva, LA Khoroshilova, KP Yanulov (1968): Sogdianite - a new mineral , In: Doklady Akademii Nauk SSSR , 182, pp. 1176–1177 ( PDF (Russian) )
- ↑ a b c d e f g h i j M. Fleischer (1969): New mineral names , In: American Mineralogist , 54, pp. 1218–1223 ( PDF, 388 kB )
- ↑ Webmineral - New Dana Classification of Cyclosilicates cyclosilicates Condensed ring
- ↑ LA Pautov, PV Khvorov, VA Muftakhov, AA Agakhanov (2000): Sogdianite and sugilite from Dara-i-Pioz massif (Tajikistan) , In: Proceedings of the Russian Mineralogical Society , Volume 129, pp. 66-79 ( abstract, PDF 556 kB )
- ^ MA Cooper, FC Hawthorne, AND ES Grew (1999): The crystal chemistry of sogdianite, a milarite-group mineral , In: American Mineralogiste , 84, pp. 764-768 ( PDF, 1.4 MB )
- ↑ Find location list for Sogdianite at the Mineralienatlas and at Mindat
- ↑ Mindat - Sogdianite from Washington Pass, Golden Horn Batholith, Okanogan Co., Washington, USA