Gmelinite

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Gmelinite-Ca, -K or -Na
Gmelinite-454055.jpg
Gmelinite from Avhellero , Larnaka , Cyprus (field of view 2 cm)
General and classification
other names

Groddeckit

chemical formula General: (Na 2 , Ca, K 2 ) 4 [Al 8 S 16 O 48 ] • 22H 2 O
Mineral class
(and possibly department) 		Silicates and Germanates - framework silicates (tectosilicates)
System no. to Strunz
and to Dana 		9.GD.05 ( 8th edition : VIII / J.26)
77.01.02
Crystallographic Data
Crystal system hexagonal
Crystal class ; symbol dihexagonal-dipyramidal; 6 / m  2 / m  2 / m
Space group P 6 3 / mmc (No. 194)Template: room group / 194
Lattice parameters see crystal structure
Formula units Z  = 1
Twinning Penetration twins according to {10 1 1}
Physical Properties
Mohs hardness 4.5
Density (g / cm 3 ) 2.02 to 2.17; calculated: 2.098
Cleavage clearly after {10 1 0}
Break ; Tenacity uneven; brittle
colour colorless, white, yellowish, greenish, light orange to salmon red
Line color White
transparency transparent to translucent
shine Glass gloss
Crystal optics
Refractive indices n ω  = 1.476 to 1.494
n ε  = 1.474 to 1.480
Birefringence δ = 0.002 to 0.014
Optical character uniaxial alternating
Other properties
Chemical behavior Easily soluble in dilute hydrochloric acid
Special features piezoelectric

Gmelinite is the collective name for a mineral from a group of chemically very similar minerals, consisting of the end members Gmelinit-Ca , Gmelinit-K and Gmelinit-Na recognized by the International Mineralogical Association (IMA) . All end links crystallize in the hexagonal crystal system with the following chemical composition:

  • Gmelinite-Na: Na 4 [Al 4 Si 8 O 24 ] · 11H 2 O (empirical formula: (Na 7.61 Ca 0.03 K 0.16 ) [Al 7.41 Si 16.49 O 48 ] · 21.51H 2 O)
  • Gmelinite-Ca: Ca 2 [Al 4 Si 8 O 24 ] · 11H 2 O (empirical formula: (Ca 2.06 Sr 1.35 Na 0.78 K 0.11 ) [Al 7.82 Si 16.21 O 48 ] · 23.23H 2 O)
  • Gmelinit-K: K 4 [Al 4 Si 8 O 24 ] · 11H 2 O (empirical formula: (K 2.72 Ca 1.67 Sr 0.39 Na 0.22 Mg 0.13 ) [Al 7.79 Si 16.32 O 48 ] · 23.52H 2 O)

There are thus chemically seen hydrous sodium - calcium - or potassium - aluminum silicates which are structurally to the tectosilicates belonging and as such a group of zeolites within the mineral class are counted the "silicates and germanates".

Gmelinite usually develops tabular, pyramidal or rhombohedral crystals with a glass-like sheen on the surface, but also occurs in the form of radial or granular mineral aggregates . In its pure form it is colorless and transparent. However, due to multiple refraction due to lattice construction defects or polycrystalline training, it can also appear white and, due to foreign admixtures, take on a yellowish, greenish or light orange to salmon red color, the transparency decreasing accordingly.

Etymology and history

Christian Gottlob Gmelin

Gmelinite was first discovered on Monte Nero near the municipality of San Pietro Mussolino in the northeast Italian province of Vicenza (Veneto) and described in 1825 by David Brewster , who named the mineral after the well-known chemist and pharmacist Christian Gottlob Gmelin (1792–1860).

Gmelinit-Ca was also first discovered on Monte Nero and in 1997 by Douglas S. Coombs et al. described. On the basis of this discovery, the gmelinit described by Brewster was modified in 1997/98 in the course of a general revision of the zeolite nomenclature by Coombs et al. renamed Gmelinit-Na as the sodium-rich end link. Gmelinit-K was proposed as the third possible, initially hypothetical, end link of the gmelinit series. The crystal structure of gmelinit-Na was first determined in 1966 by K. Fischer, but in 1982 by Ermanno Galli et al. newly defined. The structure of gmelinit-K was in 1990 by Giovanna Vezzalini et al. newly defined.

As a natural mineral formation, Gmelinit-K was first discovered in 1999 on the Alluaiw in the Lowosero Tundra massif on the Russian Kola Peninsula and also by AP Khomyakov, LI Polezhaeva and Yu. A. Malinovskiy. At the IMA, the mineral was registered under entry no. 1999-039 registered, tested and recognized as independent. The publication of the original description followed in 2001 in the magazine "American Mineralogist" published by the Mineralogical Society of America .

classification

Already in the outdated, but partly still in use 8th edition of the mineral systematics according to Strunz , the gmelinites belonged to the mineral class of "silicates and germanates" and there to the department of "tectosilicates (tectosilicates), with zeolites", where they together with bellbergite , chabazite Ca , Chabazit-K , Chabazit-Na , Chabasit-Sr , Erionit-Ca , Erionit-K , Erionit-Na , Lévyn-Ca , Lévyn-Na , Mazzit-Mg , Mazzit-Na , Offretit , Perlialith , Tschernichit and Willhendersonit die "Subgroup of Cube Zeolites I" with the system no. VIII / J.26 within the zeolite 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 gmelinites to the category of “tectosilicates with zeolitic H 2 O; Family of zeolites ”. However, this is further subdivided according to the framework structure, so that the Gmelinites can be found in the sub-section "Chains of five rings", where they form the unnamed group 9.GD.05 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the gmelinite to the class of "silicates and Germanates" and there in the department of "structural silicates: zeolite group". Here they are in the " Chabazite and allied species " with the system no. 77.01.02 to be found in the subsection "Real Zeolites".

Crystal structure

All gmelinites crystallize hexagonally in the space group P 6 3 / mmc (space group no.194) with the following lattice parameters with one formula unit per unit cell : Template: room group / 194

  • Gmelinite Na: a  = 13.756 (5)  Å and c  = 10.048 (5) Å
  • Gmelinite-Ca: a  = 13.800 (5) Å and c  = 9.964 (5) Å
  • Gmelinite-K: a  = 13.621 (3) Å and c  = 10.254 (1) Å

Education and Locations

Pale pink gmelinite with a hexagonal habit from "Two Islands" (Brothers), Parrsboro , Cumberland County, Nova Scotia, Canada
Tabular gmelinite Na from the Poudrette quarry, Mont Saint-Hilaire , Canada (field of view 2.2 mm × 2.9 mm)

Gmelinite forms in cavities in volcanic rocks containing sodium, calcium and / or potassium, such as basalt or pegmatite . As Begleitminerale can more zeolites as well as aragonite , calcite , Cancrinit , nepheline , quartz , sodalite and other minerals occur.

As a rather rare mineral formation, gmelinites can sometimes be abundant at various sites, but overall these minerals are not very common. A total of around 160 sites are known to date (as of 2013). In addition to the type locality Monte Nero, which applies to gmelinite-Na and gmelinite-C, and other places in the Veneto region , these minerals were also found on Mount Caliella near Palagonia in Sicily. Apart from its type locality Alluaiw in Russia, Gmelinit-K could only be found at San Giorgio di Perlena in the Italian province of Vicenza (Veneto).

In Germany, gmelinit is only known from Sankt Andreasberg in Lower Saxony and from Mahlscheid near Herdorf in North Rhine-Westphalia.

Other locations include Australia, Greenland, Israel, Canada, Kazakhstan, Japan, Madagascar, New Zealand, Norway, Spain, the Czech Republic, Ukraine, Hungary, the United Kingdom (UK), the United States of America (USA) and Cyprus .

See also

literature

Monographs and scientific papers
  • David Brewster : Description of gmelinite, a new mineral species. In: The Edinburgh Journal of Science. Volume 2 (1825), pp. 262–267 ( PDF 429 kB )
  • Gmelinite- (Na) , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 74.1 kB )
  • Douglas S. Coombs, Alberto Alberti, Thomas Armbruster , Gilberto Artioli, Carmine Colella, Ermanno Galli, Joel D. Grice, Friedrich Liebau , Joseph A. Mandarino , Hideo Minato, Ernest H. Nickel , Elio Passasslia, Donald R. Peacor, Simona Quartieri, Romano Rinaldi, Malcom Ross, Richard A. Sheppard, Ekkehard Tillmanns, Giovanna Vezzalini: Recommended nomenclature for zeolite minerals: report of the Subcommittee on Zeolites of the International Mineralogical Association, Commission on New Minerals and Mineral Names. In: The Canadian Mineralogist. Volume 35 (1997), pp. 1571–1606 ( PDF 3.3 MB )
  • William Alexander Deer (Ed.): Framework Silicates: Silica Minerals, Feldspathoids and the Zeolites. Geological Society of London 2004, ISBN 978-1-86239-144-4 , pp. 690-696 ( limited online availability in Google book search)
In compendia

Web links

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

Individual evidence

  1. ↑ Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties . 5th completely revised and supplemented edition. Weise, Munich 2008, ISBN 978-3-921656-70-9 .
  2. ↑ a b c d e f g h Douglas S. Coombs, Alberto Alberti, Thomas Armbruster , Gilberto Artioli, Carmine Colella, Ermanno Galli, Joel D. Grice, Friedrich Liebau , Joseph A. Mandarino , Hideo Minato, Ernest H. Nickel , Elio Passasslia, Donald R. Peacor, Simona Quartieri, Romano Rinaldi, Malcom Ross, Richard A. Sheppard, Ekkehard Tillmanns, Giovanna Vezzalini: Recommended nomenclature for zeolite minerals: report of the Subcommittee on Zeolites of the International Mineralogical Association, Commission on New Minerals and Mineral Names. In: The Canadian Mineralogist. Volume 35 (1997), pp. 1571–1606 ( PDF 3.3 MB )
  3. ^ William Alexander Deer (ed.): Framework Silicates: Silica Minerals, Feldspathoids and the Zeolites. Geological Society of London 2004, ISBN 978-1-86239-144-4 , p. 690 ( available online in the Google book search)
  4. ↑ John L. Jambor, Edward S. Grew, Andrew C. Roberts: New Mineral Names. In: American Mineralogist. Volume 87 (2002), pp. 1509–1513 ( PDF 74.4 kB ; Gmelinite-K on p. 2)
  5. ↑ Mindat - Number of localities for Gmelinite
  6. ↑ Find location list for gmelinite in the Mineralienatlas and Mindat