Klochit

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Klochit
General and classification
other names

IMA 2007-054

chemical formula K □ 2 Fe 3+ Fe 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
63.02.01a.20
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  = 10.120  Å ; c  = 14.298 Å
Formula units Z  = 2
Frequent crystal faces {0001}
Physical Properties
Mohs hardness Please complete!
Density (g / cm 3 ) calculated: 3.007
Cleavage -
colour blue
Line color Please complete!
transparency transparent
shine Glass gloss
Crystal optics
Refractive indices n ω  = 1.594
n ε  = 1.590
Birefringence δ = 0.004
Optical character uniaxial negative
Pleochroism strong: ε = light yellow; ω = dark blue

The mineral klochite is a very rarely occurring ring silicate from the milarite group with the simplified chemical composition K □ 2 Fe 3+ Fe 2+ 2 Zn 3 Si 12 O 30 . It crystallizes in the hexagonal crystal system and develops blue, six-sided platy crystals less than one millimeter in size.

Klöchit forms during the contact metamorphosis of silicate-rich foreign rock inclusions in alkali-rich basanitic magmas and has so far only been found at its type locality , the Klöch volcano in Styria , Austria .

Etymology and history

The Austrian mineral collector Walter Trattner, who discovered the mineral trattnerite named after him in 1999 , found another new mineral of the milarite group in 2000 in a quartz-rich foreign rock inclusion from the Klöch volcano near Bad Radkersburg in Styria, Austria . The mineral was first analyzed and scientifically described by Hans-Peter Bojar, Franz Walter, Christoph Hauzenberger and Walter Postl, who named it after its type locality. The results of the analysis and the chosen name were submitted to the International Mineralogical Association (IMA) for examination in 2007 (IMA entry number: 2007-054) and the mineral was recognized as independent in the same year.

classification

Klöchit is not yet listed in the outdated, but partly still in use, 8th edition of Strunz's mineral classification. Only in Stefan Weiß's "Lapis Mineral Directory", which, out of consideration for private collectors and institutional collections, is still based on the classic system of Karl Hugo Strunz , was the mineral given system no. VII / E.22-65 . So he would together with Almarudit , Armenit , Berezanskit , Brannockit , Chayesit , Darapiosit , Dusmatovit , Eifelit , Emeleusit , Faizievit , Merrihueit , Milarit , Oftedalit , Osumilith , Osumilith- (Mg) , Poudretteit , Roedderit , Shibkovit , Sogdianit , Sugilith , Trattnerit , Yagiit and Yakovenchukit- (Y) in the "Milarit-Osumilith-Gruppe" with the system no. VIII / E.22 within the division of " ring silicates (cyclosilicates)".

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the IMA, also classifies the Klöchit 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, Darapiosit, Dusmatovit, Eifelit, Friedrichbeckeit , 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 world , assigns the Klöchit 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

Klöchit is the Fe-Zn analog of Oftedalit and Agakhanovit- (Y) and the measured composition from the type locality is [12] (K 0.78 Na 0.22 ) [9] (□ 1.67 Na 0.33 ) [6] (Fe 3+ 1.19 Fe 2+ 0.45 Mn 0.27 Ca 0.04 Co 0.02 Ni 0.01 Mg 0.01 Ti 0.01 ) [4] (□ 0.25 Zn 2.63 Fe 2+ 0.10 Li 0.02 ) [Si 12 O 30 ], the coordination number of the respective position in the crystal structure being indicated in square brackets .

Crystal structure

Klöchite crystallizes in the hexagonal crystal system in the space group P 6 / mcc (space group no. 192) with the lattice parameters a  = 10.120  Å and c  = 14.298 Å as well as two formula units per unit cell . Template: room group / 192

Klochite 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 + ) and sodium (Na + ), while the 9-fold coordinated B position is unoccupied. The 6-fold coordinated A position is occupied by mixed divalent and trivalent iron cations Fe 3+ , Fe 2+ and some manganese (Mn). The tetrahedrally coordinated T2 position contains mainly zinc (Zn 2+ ), some iron (Fe 2+ ) and a few vacancies. The T1 position, which builds up the double rings, contains only silicon (Si 4+ ).

Education and Locations

Klöchit forms contact metamorphic at high temperatures around 900 ° C and low pressure in silicon-rich xenolites in alkali-rich basalts.

The only documented occurrence of Klöchite so far is its type locality , the nepheline basanite quarry near Klöch, Bad Radkersburg in the Austrian state of Styria.

There the mineral was found in cavities in a silicate-rich rock inclusion in nepheline - basanite - lava . It occurs together with quartz , sanidine , diopside , fluororichterite , titanite , enstatite , forsterite , ilmenite and mottramite .

See also

Web links

Individual evidence

  1. ↑ a b c d e f g h i j k l m n o p q r s t Hans-Peter Bojar, Franz Walter, Christoph Hauzenberger, Walter Postl: Klöchite, K □ 2 (Fe 2+ Fe 3+ ) Zn 3 [Si 12 O 30 ], a new Milarite-Type Mineral Species From The Klöch Volcano, Styria, Austria . In: The Canadian Mineralogist . tape 49 , no. 4 , August 2011, p. 1115-1124 , doi : 10.3749 / canmin.49.4.1115 ( abstract ).
  2. ↑ Webmineral - Klöchit (English)
  3. ↑ a b c d I. Fritz, B. Jandel, Walter Postl: From the depths of the volcanoes . Office for Process Engineering and Regional Development, Dr. Christian Krotscheck (BVR Verlag), Auersbach, Austria 2011, ISBN 978-3-9502374-9-8 , pp. 157 ( e-book ).
  4. ↑ Ernst AJ Burke, Frédéric Hatert: New Minerals approved in 2007 Nomenclature modifications approved in 2007 by the Commission on new Minerals, Nomenclature and Classification International Mineralogical Association . 2007, p. 10 ( main.jp [PDF; 90 kB ; accessed on September 16, 2017] IMA No. 2007-054).
  5. ^ Basalt quarry, Klöch, Bad Radkersburg, Styria, Austria