Kornerupine

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Kornerupine
Kornerupine-162065.jpg
Kornerupine crystal from Mount Riddock Station, Harts Ranges, Northern Territory, Australia
General and classification
chemical formula (□, Mg, Fe 2+ ) Al 4 (Mg 3 Al 2 ) [O 4 | (OH, O) | Si 2 O 7 | (Si (Al, B) Si) Σ3 O 10 ]
Mineral class
(and possibly department) 		Silicates and Germanates
System no. to Strunz
and to Dana 		9.BJ.50 ( 8th edition : VIII / B.31)
58.01.01.01
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol orthorhombic-dipyramidal; 2 / m  2 / m  2 / m
Space group Cmcm (No. 63)Template: room group / 63
Lattice parameters a  = 13.75  Å ; b  = 16.04 Å; c  = 6.71 Å
Formula units Z  = 4
Frequent crystal faces {110}, {100}, {010}
Physical Properties
Mohs hardness 6 to 7
Density (g / cm 3 ) measured: 3.29 to 3.35; calculated: 3.288
Cleavage good after {110}
colour colorless, white, gray, greenish, bluish, greenish brown to yellowish brown, black
Line color White
transparency transparent to translucent
shine Glass gloss, matt
Crystal optics
Refractive indices n α  = 1.660 to 1.671
n β  = 1.673 to 1.683
n γ  = 1.674 to 1.684
Birefringence δ = 0.014
Optical character biaxial negative
Axis angle 2V = measured: 3 to 48 °; calculated: 30 to 32 °

Kornerupine is a rarely occurring mineral from the mineral class of " silicates and germanates ". It crystallizes in the orthorhombic crystal system with the chemical composition (□, Mg, Fe 2+ ) Al 4 (Mg 3 Al 2 ) [O 4 | (OH, O) | Si 2 O 7 | (Si (Al, B) Si) Σ3 O 10 ] and develops mostly transparent to translucent crystals with a prismatic habit , but also radial or granular mineral aggregates .

Pure Kornerupine is colorless and transparent. However, it can appear white due to a multicrystalline (grainy) formation or lattice construction defects or it can take on a gray, greenish, bluish, greenish-brown to yellowish-brown or black color due to foreign admixtures. However, the line color is always white.

With a Mohs hardness of 6 to 7, Kornerupine belongs to the medium-hard to hard minerals and, like the reference mineral for hardness 6 orthoclase , can still be scratched with a steel file or, like the reference mineral for hardness 7 quartz , is able to scratch window glass.

Etymology and history

Kornerupine was first discovered at Qeqertarsuatsiaat (Danish Fiskenæsset) on Greenland and described in 1884 by Johannes Theodor Lorenzen (1855-1884), who named the mineral after the Danish geologist Andreas Kornerup .

classification

In the meantime outdated, but still in use 8th edition of the mineral classification by Strunz of Kornerupin belonged to the mineral class of "silicates and Germanates" and then to the Department of " island silicates with tetrahedral foreign anions (Neso-Subsilikate)" where he collaborated with Boralsilit , Dumortierite , Grandidierite , Harkerite , Holtite , Magnesiodumortierite , Ominelite , Prismatin and Werdingite formed a separate group.

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 assigns the Kornerupine to the class of "silicates and germanates" and there in the department of " group silicates (sorosilicates)". This department is, however, further subdivided according to the type of silicate group formation and the size of the cations involved , so that the mineral is classified according to its composition in the subdivision of “group silicates with Si 3 O 10 , Si 4 O 11 etc. anions; Cations in octahedral [6] and / or greater coordination ”can be found, where together with prismatin it forms the unnamed group 9.BJ.50 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Kornerupine to the class of "silicates and Germanates", but there in the more finely subdivided division of "group silicates: insular, mixed, individual and larger tetrahedral groups". Here he is the namesake of the "Kornerupin group" with the system no. 58.01.01 and the other member Prismatin within the subdivision of “ Group silicates: insular, mixed, single and larger tetrahedral groups with cations in [4] and higher coordination; Single and double groups (n = 1,2) ”.

Crystal structure

Kornerupine crystallizes orthorhombically in the space group Cmcm (space group no. 63) with the lattice parameters a  = 13.75  Å ; b  = 16.04 Å and c  = 6.71 Å and 4 formula units per unit cell . Template: room group / 63

Education and Locations

Green, transparent Kornerupine in gem quality from the Horombe region, Fianarantsoa province , Madagascar (size: 9 cm × 4 cm × 4 cm)

Kornerupine mostly forms in boron-rich volcanic and sedimentary rocks that have been heavily stressed metamorphically and form amphibolite or granulite facies . Accompanying minerals include andalusite , biotite , cordierite , dumortierite , grandidierite , hematite , ilmenite , corundum , kyanite , magnetite , phlogopite , rutile , sapphirin , sillimanite , spinel and various tourmalines .

In total, Kornerupine has so far (as of 2011) been detected at 44 sites. In addition to its type locality Qeqertarsuatsiaat ( Fiskenæsset ), where the largest known crystals with a diameter of up to 23 cm were found, the mineral occurred on Greenland on Bjørnesund near Sarfaq in the Kitaa district .

Other sites are in Enderbyland and the Lützow-Holm-Bucht in East Antarctica; at Mount Riddock Station and the Strangways Ranges in the Northern Territory of Australia; at Ongaing , near the city of Mogok in the Mandalay Division of Myanmar (formerly Burma); at Lac-Sainte-Marie in the Outaouais region of Canada ; at Jixi in China; on the Rio Mayo in the Municipal de Mercaderes in the Colombian municipality of Cauca ; at Varpaisjärvi and Kittilä in Finland; on Lasamba Hill and Mangari in the Kenyan province of Coast ; at Ambovombe , Betroka and Mahafaly in the province of Toliara in Madagascar; at Arendal , Froland and Risør in Aust-Agder Province and at Bamble in Telemark Province in Norway; on Chilapila Hill in the Copperbelt in Zambia; near Dobšiná in Slovakia; at Port Shepstone , Soutpansberg and Namaqualand in South Africa; near Weligama in the Matara district in Sri Lanka; in the Pamir Mountains in Tajikistan; on Mautia Hill in the Dodoma region of Tanzania; in the Labwor Hills in the district of Kotido in Uganda ; at Mase Mountain in Morris County and at Greenwood Lake in New Jersey, at Lyonsdale in Lewis County and at Warrensburg in the county of the same name in New York and at Moses Rock in San Juan County in Utah.

See also

literature

  • Joh. Lorenzen: Investigations of Greenlandic minerals . In: P. Groth (Ed.): Journal for crystallography and mineralogy . tape 11 . Verlag von Wilhelm Engelmann, Leipzig 1886, p. 317 ( rruff.info [PDF; 246 kB ; accessed on April 19, 2018] Original title: Undersögelse af Mineralier fra Grönland . In: Meddelelser om Greenland 7 , Copenhagen 1884).

Web links

Commons : Kornerupine  - collection of images, videos and audio files

Individual evidence

  1. ↑ a b c d e 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.  593 .
  2. ↑ Webmineral - Kornerupine (English)
  3. ↑ a b Kornerupine . 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; 77  kB ]).
  4. ↑ a b c d e Mindat - Kornerupine (English)
  5. ↑ Lorenzen . In: Christian Blangstrup (Ed.): Salmonsens Konversationsleksikon . 2nd Edition. tape  15 : Kvadratrod – Ludmila . JH Schultz Forlag, Copenhagen 1923, p. 1045 (Danish, runeberg.org ).
  6. ↑ Mindat - number of locations
  7. ↑ Find location list for Kornerupine in the Mineralienatlas and Mindat