Darapiosit

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Darapiosit
General and classification
other names

Darapiozite

chemical formula KNa 2 Mn 2+ 2 Zn 2 Li 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.03
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  = 10.262  Å ; c  = 14.307 Å
Formula units Z  = 2
Physical Properties
Mohs hardness 5
Density (g / cm 3 ) measured: 2.92
Cleavage Please complete!
colour colorless, white, rarely bluish or bluish, pale purple
Line color Please complete!
transparency transparent
shine Please complete!
Crystal optics
Refractive indices n ω  = 1.580
n ε  = 1.575
Birefringence δ = 0.005
Optical character uniaxial negative
Pleochroism blue variety: violet ∥ ω, blue ∥ ε

The mineral darapiosit is a very rarely occurring ring silicate from the milarite group and has the idealized chemical composition K Na 2 Mn 2+ 2 Zn 2 Li Si 12 O 30 . It crystallizes in the hexagonal crystal system and develops colorless, isometric crystals of less than one centimeter in size.

Darapiosit forms in alkali-rich pegmatites at low pressure (<2 kbar ) and average temperatures around 450–500 ° C. It is so far only on its type locality , the moraines of the Darai-Pioz- glacier in Alay Mountains in Tajikistan have been found.

Etymology and history

Darapiosit was discovered in the moraines of the Darai-Pioz- glacier in Alay Mountains in Tajikistan described and 1976 by YI Semenov, VD Dusmatov, AP Khomyakov, AA Voronkov & MY Kazakova as a new mineral of Milaritgruppe. They named the mineral after the place where it was found, Dara-Pioz in northern Tajikistan, Darapiosit.

classification

In the outdated, but still partially common 8th edition of the mineral classification by Strunz Darapiosit belongs Almarudit , Armenit , Brannockit , Berezanskit , Chayesit , Dusmatovit , 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 darapiosit 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 . It includes Agakhanovit-Ce , Almarudit, Armenit, Berezanskit, Brannockit, Chayesit, Eifelit , Dusmatovit, Friedrichbeckeit , Klöchit , Merrihueit, Milarit, Oftedalit, Osumilith, Osumilith- (Mg), Poudretteit, Roedderite, Shibkovite , 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 world , assigns the darapiosit 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

Darapiosit has the measured composition [12] K [9] (Na 1.22 K 0.36 □ 0.42 ) [6] (Mn 2+ 1.54 Zr 0.30 Y 0.23 Mg 0.03 ) [ 4] (Li 1.53 Zn 1.15 Fe 2+ 0.31 ) [4] Si 11.98 O 30 , the coordination number of the respective position in the crystal structure being given in square brackets .

The idealized composition of the Darapiosit terminal was controversial. In 1976, Semenov and co-workers gave the simplified composition as (K, Na) 3 Zr Li (Mn, Zn) 2 Si 12 O 30 . Cooper et al. 1999 defined darapiosit as K Na 2 Mn 2+ 2 LiZn 2 Si 12 O 30 and the group of Sokolova and Hawthorne one year later as K Na 2 Mn 2+ Zr 4+ Li 3 Si 12 O 30 .

Hawthorne, who was involved in the publication of both contradicting formulas, published a general scheme in 2002 for determining the end-link compositions of complex mixed crystals and confirmed the darapiosit formula of Cooper's team: K Na 2 Mn 2+ 2 LiZn 2 Si 12 O 30 .

In the current IMA list (2019), the simplified composition is given as KNa 2 Mn 2 (Li 2 ZnSi 12 ) O 30 . This composition is not electrically neutral and has an excess of one negative charge. The structural study by Giovanni Ferraris et al. (1999), in which this formula is not mentioned, is listed as the source.

The measured compositions of darapiosit correspond to mixed crystals of essentially darapiosit with sogdianite (Zr incorporation) and a hypothetical end link of the composition K □ 2 M 3+ 2 Zn 2 Li Si 12 O 30 (Y 3+ incorporation).

Crystal structure

Darapiosit crystallizes in the hexagonal crystal system in the space group P 6 / mcc (space group no. 192) with the lattice parameters a  = 10.262  Å and c  = 14.307 Å as well as two formula units per unit cell .  Template: room group / 192

Darapiosit 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 is not completely occupied with sodium (Na + ) and potassium. Manganese (Mn 2+ ), zirconium (Zr 4+ ), yttrium (Y 3+ ) and traces of magnesium (Mg 2+ ) fill the 6-fold coordinated A position. The tetrahedrally coordinated T2 position contains mainly lithium (Li + ) as well as zinc (Zn 2+ ) and some iron ((Fe 2+ )). The T1 position, which builds up the 6 double rings, only contains silicon (Si 4+ ).

Education and Locations

Darapiosit forms in alkali-rich , H 2 O-undersaturated pegmatites at low pressure (<2 kbar ) and temperatures around 450–500 ° C.

So far Darapiosit was only at its type locality , the Darai-Pioz- glacier in Alay Mountains in Tajikistan found and documented, where in quartz aggregates in the moraines occur. Darapiosit occurs here together with quartz , the sodium pyroxene aegirine , eudialyte , schizolite , the lithium mica polylithionite , the milarite group mineral sogdianite as well as microcline and relictic reed morgnerite .

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

  • EI Semenov, VD Dusmatov, AP Khomyakov, AA Voronkov, ME Kazakova: Darapiosite, a new mineral of the milarite group . In: Zapiski Vsesoyuznogo Mineralogicheskogo Obshchestva . tape 104 , no. 5 , 1975, p. 583-585 (Russian, rruff.info [PDF; 185 kB ; accessed on December 10, 2019]).
  • Michael Fleischer , Adolf Pabst , Louis J. Cabri: New mineral names . In: American Mineralogist . tape 61 , 1976, p. 1053-1056 (English, rruff.info [PDF; 410 kB ; accessed on December 10, 2019]).
  • Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 714 (first edition: 1891).

Web links

Individual evidence

  1. ^ Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  614 (English).
  2. ^ A b c Mark A. Cooper, Frank C. Hawthorne, Edward S. Grew: The crystal chemistry of sogdianite, a milarite-group mineral . In: American Mineralogist . tape 84 , 1999, pp. 767 ( rruff.info [PDF; 1.5 MB ; accessed on December 10, 2019] Table 7).
  3. ↑ a b c d Frank C. Hawthorne: The Use Of End-Member Charge-Arrangements In Defining New Mineral Species And Heterovalent Substitutions In Complex Minerals . In: The Canadian Mineralogist . tape 40 , 2002, p. 699–710 , doi : 10.2113 / gscanmin.40.2.699 (English, researchgate.net [PDF; 357 kB ; accessed on December 10, 2019]).
  4. ↑ a b c d e f g h i j k l Ye.I. Semenov, VD Dusmatov, AP Khomyakov, AA Voronkov & M. Ye. Kazakova: Darapiosite, a new mineral of the milarite group . In: Zapiski Vsesoyuznogo Mineralogicheskogo Obshchestva . tape 104 , 1976, pp. 583-585 , doi : 10.1080 / 00206817609471289 (English).
  5. ↑ a b c d e f g h i j k Michael Fleischer , Adolf Pabst , Louis J. Cabri: New mineral names . In: American Mineralogist . tape  61 , 1976, p. 1053-1056 (English, rruff.info [PDF; 410 kB ; accessed on December 10, 2019]).
  6. ↑ David Barthelmy: Darapiosite Mineral Data. In: webmineral.com. Retrieved December 10, 2019 .
  7. ↑ a b c d e f g h i j k Giovanni Ferraris, Mauro Prencipe, Leonid A. Pautov, Elena V. Sokolova: The Crystal Structure Of Darapiosite And A Comparison With Li And Zn-Bearing Minerals Of The Milarite Group . In: The Canadian Mineralogist . tape 37 , 1999, pp. 769-774 (English, rruff.info [PDF; 1.4 MB ; accessed on December 10, 2019]).
  8. ↑ Webmineral - New Dana Classification of Cyclosilicates cyclosilicates Condensed ring
  9. ^ Elena V. Sokolova, Frank C. Hawthorne, Leonid A. Pautov: The Crystal Chemistry Of Li-bearing Minerals With The Milarite-Type Structure: The Crystal Structure Of End-Member Sogdianite . In: The Canadian Mineralogist . tape 38 , 2000, pp. 858 (English, [1] [PDF; 698 kB ; accessed on December 10, 2019] Table 8).
  10. ↑ Malcolm Back, William D. Birch, Michel Blondieau and others: The New IMA List of Minerals - A Work in Progress - Updated: November 2019. (PDF 1720 kB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, November 2019, accessed December 10, 2019 .
  11. ↑ a b Type locality Dara-i-Pioz Glacier (Dara-Pioz), Districts of Republican Subordination, Tajikistan. In: mindat.org. Hudson Institute of Mineralogy, accessed December 10, 2019 .