Koashvit

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Koashvit
General and classification
other names
  • IMA 1973-026
  • Koašvit
chemical formula
  • Na 6 CaTiSi 6 O 18
  • Na 6 (Ca, Mn, Fe 3+ ) (Ti, Fe 3+ ) [Si 6 O 18 ]
  • Na 6 (Ca, Mn 2+ ) (Fe 3+ , Ti) [Si 6 O 18 ] · H 2 O
Mineral class
(and possibly department) 		Silicates and Germanates
System no. to Strunz
and to Dana 		9.CJ.20 ( 8th edition : VIII / E.16)
61.01.02b.02
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol orthorhombic-dipyramidal; 2 / m  2 / m  2 / m
Space group Pmnb (No. 62, position 2)Template: room group / 62.2
Lattice parameters a  = 10.18  Å ; b  = 20.90 Å; c  = 7.34 Å
Formula units Z  = 4
Physical Properties
Mohs hardness 6 (VHN 20 = 680-740)
Density (g / cm 3 ) measured: 2.98 to 3.02; calculated: 3.069
Cleavage is missing
Break ; Tenacity shell-like
colour light yellow to brownish yellow
Line color White
transparency transparent
shine Glass gloss
Crystal optics
Refractive indices n α  = 1.637
n β  = 1.643
n γ  = 1.648
Birefringence δ = 0.011
Optical character biaxial negative
Axis angle 2V = 82 ° to 84 ° (measured); 84 ° (calculated)

Koashvit is a very rare mineral from the mineral class of " silicates and germanates " with the idealized chemical composition Na 6 CaTiSi 6 O 18 and is therefore chemically a sodium - calcium - titanium silicate.

Koashvite crystallizes in the orthorhombic crystal system , but has so far only been found in the form of flattened mineral aggregates and grown in as small veins in ultrabasic pegmatite . The mineral is transparent, light yellow in color and has a glass-like sheen on the surface .

Etymology and history

Koashvit was first discovered in 1965 in a drill core at a depth of around 150 meters. The borehole was sunk on the eastern slope of the Koaschwa near the open-cast mine of the same name. The Koaschwa belongs to the mountain range of the Chibinen on the Russian Kola peninsula belonging to the Murmansk Oblast . The mineral was scientifically described by Yu. L. Kapustin, ZV Pudovkina, AV Bykova and GV Lyubomilova, who named it after its type locality . The complete mineral description and chosen name have been submitted to the International Mineralogical Association (IMA) for review (IMA accession number : 1973-026 ) and approved. The publication of the new discovery followed in 1974 in Russian in the science magazine Zapiski Vsesoyuznogo Mineralogicheskogo Obshchestva and a year later, translated into English by Michael Fleischer , in the International Geology Review .

Type material of the mineral is in the Fersman Museum in Moscow under the catalog no. 75148 and kept at Mines ParisTech in Paris.

classification

Already in the outdated, but partly still in use 8th edition of the mineral systematics according to Strunz , the koashvite belonged to the mineral class of "silicates and germanates" and there to the department of "ring silicates (cyclosilicates)", where it together with Imandrite , Kazakovit , Kapustinit , Litvinskit , Lovozerite , Petarasite , Tisinalite and Zirsinalite the "Lovozerite group" with the system no. VIII / E.16 .

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 Koashvit in the category of "ring silicates (cyclosilicates)". This is, however, further subdivided according to the structure of the rings including the possible presence of island-like, complex anions , so that the mineral can be found according to its structure in the subsection "[Si 6 O 18 ] 12− -six-simple rings without island-like, complex anions" is where, together with Imandrit, the "Imandrit-Koashvit-Gruppe" with the system no. 9.CJ.20 forms without further members.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Koashvit to the class of "silicates and Germanates", but there in the somewhat more finely subdivided division of "ring silicates: six rings". Here he is together with Imandrite, Petarasit and Litvinskit in the " Lovozeritgruppe (Orthorhomic and Monoclinic Subgroup) " with the system no. 61.01.02b within the subdivision “ Ring Silicates : Six Rings with Si 6 O 18 Rings; possible (OH) and Al substitution ”.

Crystal structure

Koashvite crystallizes orthorhombically in the space group Pmnb (space group no. 62, position 2) with the lattice parameters a  = 10.18  Å ; b  = 20.90 Å; c  = 7.34 Å and 4 formula units per unit cell . Template: room group / 62.2

Education and Locations

Koashvite is formed by the displacement of Lomonosovite and is found in the form of small veins in ultrabasic pegmatite . In addition to lomonosovite , there are also natrophosphate , pectolite and villiaumite as accompanying minerals .

The most important rocks at the Koaschwa type locality are apatite - nephelinite with carbonatite , urtite and foidolite . The open pit, which is still active (as of 2017), is known as a rich deposit in which 29 minerals alone were discovered for the first time and a total of 107 minerals and varieties were known.

Other previously known sites are the river valley of the Vuonnemiok , the mountain Raswumtschorr and the shaft Material'naya on the mountain Yukspor in the Chibinen as well as the mountain Karnassurt in the Lowosero-Tundra .

See also

literature

  • Yu. L. Kapustin, ZV Pudovkina, AV Bykova, GV Lyubomilova: Koashvit, novyy mineral . In: Zapiski Vsesoyuznogo Mineralogicheskogo Obshchestva . tape 103 , 1974, pp. 559-566 (Russian).
  • Michael Fleischer : Koashvite, a new mineral . In: International Geology Review . tape 17 , no. 6 , 1975, p. 654-660 , doi : 10.1080 / 00206817509471647 .
  • Michael Fleischer, GY Chao, Ikiro Kato: New Mineral Names . In: American Mineralogist . tape 60 , no. 5-6, 1 , 1975, pp. 485–489 ( minsocam.org [PDF; 623 kB ; accessed on November 28, 2017]).
  • Igor V. Pekov, Sergey V. Krivovichev, Andrey A. Zolotarev, Viktor N. Yakovenchuk, Thomas Armbruster, Yakov A. Pakhomovsky: Crystal chemistry and nomenclature of the lovozerite group . In: European Journal of Mineralogy . tape 21 , 2009, p. 1061-1071 ( main.jp [PDF; 1,2 MB ; accessed on November 29, 2017]).

Web links

Individual evidence

  1. ↑ Hans Jürgen Rösler : Textbook of Mineralogy . 4th revised and expanded edition. German publishing house for basic industry (VEB), Leipzig 1987, ISBN 3-342-00288-3 , p.  801 .
  2. ↑ a b IMA / CNMNC List of Mineral Names; September 2017 (PDF 1.67 MB)
  3. ^ A b c 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 .
  4. ↑ a b c Stefan Weiss: The large Lapis mineral directory. All minerals from A - Z and their properties . 6th completely revised and supplemented edition. Weise, Munich 2014, ISBN 978-3-921656-80-8 .
  5. ↑ a b c d Koashvite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 75  kB ; accessed on November 28, 2017]).
  6. ↑ Webmineral - Koashvite (English)
  7. ↑ a b c d e Mindat - Koashvite (English)
  8. ↑ Mineralienatlas : type locality Koashva pit
  9. ↑ Mindat - type locality Koashva Open Pit (Vostochnyi Mine)
  10. ↑ Find location list for Koashvit in the Mineralienatlas and in Mindat