Cancrinite

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Cancrinite
Cancrinite-Sodalite-Nepheline-222524.jpg
Cancrinite (yellow), nepheline (white) and biotite (black) from Dennis Hill, Litchfield, Kennebec County, Maine, USA
General and classification
chemical formula
  • (Na, Ca, □) 8 (Al 6 Si 6 ) O 24 (CO 3 , SO 4 ) 2 · 2H 2 O
  • Na 6 Ca 2 [(CO 3 ) 2 | Al 6 Si 6 O 24 ] • 2H 2 O
  • (Na, Ca, □) 8 [(CO 3 , SO 4 ) 2 | (AlSiO 4 ) 6 ] • 2H 2 O
Mineral class
(and possibly department) 		Framework silicates (tectosilicates); Cancrinite group
System no. to Strunz
and to Dana 		9.FB.05 ( 8th edition : VIII / F.05)
76.02.05.03
Similar minerals Sodalite , Leucite , Analcim , Nosean , Haüyn
Crystallographic Data
Crystal system hexagonal
Crystal class ; symbol hexagonal-pyramidal; 6th
Space group P 6 3 (No. 173)Template: room group / 173
Lattice parameters a  = 12.59  Å ; c  = 5.12 Å
Formula units Z  = 1
Physical Properties
Mohs hardness 5 to 6
Density (g / cm 3 ) measured: 2.42 to 2.51; calculated: [2.49]
Cleavage perfect after {10 1 0}, indistinct after {0001}
Break ; Tenacity uneven; brittle
colour colorless, white, light blue to light gray blue, yellow, orange, reddish
Line color White
transparency transparent to translucent
shine Greasy luster, glass luster, pearlescent luster
Crystal optics
Refractive indices n ω  = 1.507 to 1.528
n ε  = 1.495 to 1.503
Birefringence δ = 0.012 to 0.025
Optical character uniaxial alternating
Other properties
Chemical behavior soluble in warm hydrochloric acid

Cancrinit is a rather rare mineral from the mineral class of "silicates and germanates". It crystallizes in the hexagonal crystal system with the chemical composition (Na, Ca, ☐) 8 [(CO 3 , SO 4 ) 2 | (AlSiO 4 ) 6 ] · 2H 2 O and develops prismatic crystals or granular, massive aggregates in the colors white , yellow, orange or blue. Colorless crystals are also known. Cancrinit is one of the foids .

Etymology and history

Cancrinit was first discovered in the area of ​​the River Miass in the Russian Oblast of Chelyabinsk and described in 1839 by Gustav Rose , who named the mineral after the Russian Minister Georg Cancrin (1774-1845).

classification

Already in the now outdated 8th edition of the mineral classification by Strunz of Cancrinit belonged to the mineral class of "silicates and Germanates" and then to the Department of " framework silicates (tectosilicates)" where he collaborated with Afghanit , Davyn , Mikrosommit , Vishnevite and Wenkit the " Cancrinit series “with the system no. VIII / F.05 .

In the Lapis mineral directory according to Stefan Weiß, which, out of consideration for private collectors and institutional collections, is still based on this old form of Karl Hugo Strunz's system , the mineral was given the system and mineral number. VIII / J.09-10 . In the "Lapis Classification" this also corresponds to the "framework silicates" department where Cancrinit with Afghanit, Alloriit , Balliranoit , Biachellait , Bystrit , Carbobystrit , Cancrisilit , Davyn, Depmeierit , Fantappièit , Farneseit , Franz Init , Giuseppettit , Hydroxycancrinit , Kircherit , Kyanoxalith , Liottite , Marinellit , Mikrosommit, Pitiglianoit , Quadridavyn , Sacrofanite , Tounkit , Vishnevite and Wenkit the "cancrinite group" formed (as 2018).

The 9th edition of Strunz's mineral systematics, valid since 2001 and updated by the International Mineralogical Association (IMA) until 2009, classifies cancrinite in the more finely subdivided division of “tectosilicates without zeolitic H 2 O”. This is further subdivided according to the possible presence of further anions , so that the mineral can be found according to its composition in the sub-section “Tectosilicates with additional anions”, where the “Cancrinite group” with the system no. 9.FB.05 and the other members Afghanit, Alloriit, Balliranoit, Biachellait, Bystrite, Cancrisilit, Davyn, Fantappièit, Farneseit, Franzinit, Giuseppettit, Hydroxycancrinit, Kyanoxalith, Liottit, Marinellit, Mikrosommit, Pitivianoit, Quadridanit, Tacrofoun forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns cancrinite to the class of "silicates and germanates" and there in the department of "structural silicates: Al-Si lattice". Here he is also the namesake of the " Cancrinit group " with the system no. 76.02.05 can be found in the sub-section "Framework silicates: Al-Si lattices, feldspar representatives and related species".

Crystal structure

An early structural proposal was published in 1930 by Linus Pauling , where he suggested the space group P 6 3 / mmc (space group no. 194) . The Japanese researchers Kozu and Takane described the structure in the space group P 6 3 (no. 173) and reported for the first time about a one-dimensional canal system parallel to the crystallographic c-axis. Their proposed structure, however, showed unrealistic Si-Si and Si-Al distances. In 1962 Jarchow succeeded in defining the structure of the space group P 6 3 . Template: room group / 194Template: room group / 173Template: room group / 173

  • Fig. 1: Connection of two cancrinite cages

  • Fig. 2: Projection of the cancrinite structure along the crystallographic c-axis

The cancrinite structure can be described as a hexagonal closest packing of six Si-Al rings in the direction of [0001]. This creates characteristic cage structures due to the stacking. The cage is shown in Figure 1. The points correspond to the positions of the silicon or aluminum atoms in the framework between which, approximately in the middle of the lines, the oxygen atoms are located. These cages are referred to as epsilon cages in zeolite chemistry. The spatial arrangement of the cages, as shown in Figure 2, leads to the formation of a one-dimensional channel system in the direction of the crystallographic c-axis. The elements aluminum , silicon and oxygen form the cages of the framework. The sodium cations are located partly in the cages and partly in the ducts. CO 3 - anions are found only in the channels.

Education and Locations

Like sodalite , cancrinites crystallize from magmas with a medium to low SiO 2 content and appear here alongside other foids .

Locations include Laacher See in Germany , Bancroft / Ontario and Québec in Canada , Norway , Romania , the Russian Federation , and Litchfield / Maine in the USA .

use

In science, synthetic cancrinites, whose composition often deviates from that of the mineral, serve as a model system for zeolites. The cancrinite epsilon cage is a structural component of zeolite L.

See also

literature

Web links

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

Individual evidence

  1. ↑ Malcolm Back, William D. Birch, Michel Blondieau and others: The New IMA List of Minerals - A Work in Progress - Updated: September 2019. (PDF 2672 kB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, September 2019, accessed December 25, 2019 .
  2. ↑ a b Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties. Status 03/2018 . 7th, completely revised and supplemented edition. Weise, Munich 2018, ISBN 978-3-921656-83-9 .
  3. ↑ a b c d 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.  697 (English).
  4. ↑ a b c d e f g Cancrinite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 (English, handbookofmineralogy.org [PDF; 69  kB ; accessed on December 25, 2019]).
  5. ↑ a b c Cancrinite. In: mindat.org. Hudson Institute of Mineralogy, accessed December 25, 2019 .
  6. ↑ Gustav Rose: Ueber den Sodalith und Cancrinit , in: Journal for practical chemistry , Volume 17, published by Johann Ambrosius Barth, Leipzig 1839, p. 348 in the Google book search
  7. ↑ Ernest H. Nickel, Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF 1816 kB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed December 25, 2019 .