Dusmatovite

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Dusmatovite
General and classification
chemical formula K Na □ Mn 2+ 2 Zn 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.11
Crystallographic Data
Crystal system hexagonal
Crystal class ; symbol dihexagonal-dipyramidal; 6 / m  2 / m  2 / m
Space group P 6 / mcc (No. 192)Template: room group / 192
Lattice parameters a  = 10.218  Å ; c  = 14.292 Å
Formula units Z  = 2
Physical Properties
Mohs hardness 4.5
Density (g / cm 3 ) measured: 2.96, calculated: 2.978
Cleavage no
colour dark blue, violet blue
Line color Light Blue
transparency translucent
shine Glass gloss
Crystal optics
Refractive indices n ω  = 1.590
n ε  = 1.586
Birefringence δ = 0.004
Optical character uniaxial negative
Pleochroism violet parallel ω, light blue parallel ε

The mineral Dusmatovite is a very rarely occurring ring silicate from the milarite group and has the idealized chemical composition K Na □ Mn 2+ 2 Zn 3 Si 12 O 30 . It crystallizes in the hexagonal crystal system and develops dark blue crystals and aggregates.

Etymology and history

Was discovered Dusmatovit in the moraines of the Darai-Pioz- glacier in Alay Mountains in Tajikistan and 1996. LA Pautov, AA Agakhanov, EV Sokolova, AI Ignatenko as a new mineral of Milaritgruppe. They named the mineral after the Tajik geologist and mineralogist Vyacheslav Djuraevitch Dusmatov (1936-2004) in recognition of his work in the Darai-Pioz region. Dusmatov was involved in the first description of numerous new minerals from the Darai-Pioz glacier, including sogdianite and darapiosit from the milarite group.

classification

In the outdated, but still partially common 8th edition of the mineral classification by Strunz Dusmatovit belongs Almarudit , Armenit , Brannockit , Berezanskit , Chayesit , Darapiosit , Emeleusit , Faizievit , Merrihueit , Oftedalit , Osumilith , Osumilith- (Mg) , Poudretteit , Roedderit , Sogdianite , sugilite , trattnerite and yagiite to the general division of " ring silicates (cyclosilicates)" in the " milarite-osumilite group " with system no. VIII / E.22 .

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 Dusmatovite 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 . Therein it is part of Agakhanovit- (Y) , Almarudit, Armenit, Berezanskit, Brannockit, Chayesit, Eifelit , Darapiosit, Friedrichbeckeit , Klöchit , Merrihueit, Milarit, Oftedalit, Osumilith, Osumilith- (Mg), Poudretteit, Roedderit, Shibkovit , Sogdianit, Sugilite, trattnerite and yagiite to the " milarite group " with the system no. 9.CM.05 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking area , also assigns Dusmatovite to the class of "silicates and Germanates", although there it is 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

Dusmatovite is the Mn 2+ equivalent of Klöchit or Shibkovite and has the measured composition [12] K [9] (Na 0.66 K 0.35 ) [6] (Mn 1.48 Zr 0.16 Y 0, 17 ) [4] (Zn 2.17 Li 0.74 ) [4] Si 12 O 30 , where the coordination number of the respective position in the crystal structure is given in square brackets .

The composition of the Dusmatovit end link was controversial. Cooper et al. defined Dusmatovite in 1999 as a K analog of Darapiosit with the formula [12] K [9] K 2 [6] Mn 2+ 2 [4] (Zn 2 Li) [4] Si 12 O 30 . A year later, the group of Sokolova and Hawthorne described Dusmatovite as the manganese equivalent of Klöchit and Shibkovite with the formula [12] K [9] (□ Na) [6] Mn 2+ 2 [4] Zn 3 [4] Si 12 O 30 .

Hawthorne, who was involved in the publication of both contradicting formulas, published a general scheme for determining the end link compositions of complex mixed crystals in 2002 and confirms the Dusmatovite formula of Sokolova's team: [12] K [9] (□ Na) [6] Mn 2+ 2 [4] Zn 3 [4] Si 12 O 30 .

The measured compositions of Dusmatovite correspond to mixed crystals of Dusmatovite with Sogdianite (Zr incorporation) and a hypothetical Y-Li end link with the composition K Na 2 Y 3+ 2 Li 3 Si 12 O 30 (Y 3+ incorporation).

Crystal structure

Dusmatovite crystallizes in the hexagonal crystal system in the space group P 6 / mcc (space group no. 192) with the lattice parameters a  = 10.218  Å and c  = 14.292 Å as well as two formula units per unit cellTemplate: room group / 192

Dusmatovite is isotypic to milarite , ie it crystallizes with the same structure as milarite. The 12-fold coordinated C-position is fully occupied with potassium (K + ), the 9-fold coordinated B-position half with sodium (Na + ) and potassium. Manganese (Mn 2+ ), zirconium (Zr 4+ ) and yttrium (Y 3+ ) fill the 6-fold coordinated A position. The tetrahedrally coordinated T2 position contains predominantly zinc (Zn 2+ ) and some lithium (Li + ). The T1 position, which builds up the 6 double rings, only contains silicon (Si 4+ ).

Education and Locations

So far Dusmatovit was only at its type locality , the Darai-Pioz- glacier in Alay Mountains in Tajikistan found and documented, where it Pegmatitbruchstücken in the moraines occur. Dusmatovit occurs here, together with quartz and microcline , and the sodium pyroxene Aegirin , Tadzhikit- (Y) , Kupletskit , Hyalotekit , Betafit and the lithium Glimmer Polylithionit occurs.

This very mineral-rich site represents the type locality of 35 minerals (as of 2016), 5 of them from the milarite group alone: Berezanskite , Darapiosit , Dusmatovite, Shibkovite and Sogdianite . Furthermore, the milarite group minerals milarite, osumilite and sugilite were detected here.

See also

literature

Web links

Individual evidence

  1. a b c 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, p. 858, Table 8 ( PDF, 698 kB )
  2. a b c d FC Hawthorne (2002): The Use Of End-Member Charge-Arrangements In Defining New Mineral Species And Heterovalent Substitutions In Complex Minerals . In: The Canadian Mineralogist , 40, pp. 699–710 ( PDF (309 kB) )
  3. a b Webmineral - Dusmatovit (English)
  4. a b c d e f g EV Sokolova, LA Pautov, VA Zharikov (1995): Crystal structure of Dusmatovite In: Doklady Physics , 40, pp. 53–506 ( PDF, 514 kB )
  5. a b c d e f g h i j k l m n JL Jambor, NN Perstev, And AC Roberts (1997): New Mineral Names - Dusmatovite In: American Mineralogist , 82, p. 430 ( PDF, 89.8 kB )
  6. ^ MA Cooper, FC Hawthorne, AND ES Grew (1999): The crystal chemistry of sogdianite, a milarite-group mineral , In: American Mineralogiste , 84, p. 767, table 7 ( PDF, 1.4 MB )
  7. Darai-Pioz Glacier (Dara-i-Pioz; Dara-Pioz), Alai Range (Alayskiy), Tien Shan Mtn, Region of Republican Subordination, Tajikistan