User:Strickja/Gmelinite-Na
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| Gmelinite-Na | |
|---|---|
 Gmelinite from Flinders, Victoria, Australia. Specimen size 2.8 cm. | |
| General | |
| Category | Silicate mineral |
| Formula (repeating unit) | Na4(Si8Al4)O24.11H2O[1] |
| Strunz classification | 8/J.26-50 or 9.GD.05 |
| Dana classification | 77.1.2.6 |
| Crystal system | Hexagonal 6/m 2/m 2/m Dihexagonal Dipyramidal |
| Identification | |
| Formula mass | 2,000.77 g |
| Color | Colourless, white, yellow, orange, pale green, pink, red, brown and grey |
| Crystal habit | Hexagonal plates, or short prisms, showing hexagonal dipyramids, pyramids and basal pinacoid. {1010}, {1011} and {0001} dominant. May also be tabular or rhombohedral. Crystals are striated parallel to (0001) |
| Twinning | Interpenetrant twins common[2]on {1011}. The twins consist of four individuals, three are at 90° to the other and at 60° to each other[3] |
| Cleavage | Good on {1010} |
| Fracture | Conchoidal |
| Tenacity | Brittle |
| Mohs scale hardness | 4½ |
| Luster | Dull to vitreous |
| Streak | White |
| Diaphaneity | Transparent, translucent or opaque |
| Specific gravity | 2.04 to 2.17 |
| Optical properties | Uniaxial (-) |
| Refractive index | nω = 1.476 - 1.494, nε = 1.474 - 1.480[2] |
| Birefringence | δ = 0.002 - 0.014 |
| Solubility | Soluble in cold 10% HCl. |
| Other characteristics | Piezoelectric. Barely detectable radioactivity. As with all zeolites, water is released on heating, and almost all has been expelled by 400 °C. |
| References | [4][5] |
Gmelinite-Na is a zeolite and the commonest member of the gmelinite series, gmelinite-Ca, gmelinite-K and gmelinite-Na. It is closely related to the very similar mineral chabazite, . It was named as a single species in 1825 after Christian Gottlob Gmelin (1792-1860) professor of chemistry and mineralogist from Tubingen, Germany, and in 1997 it was raised to the status of a series[6].
Gmelinite-Na has been synthesised from Na-bearing aluminosilicate gels[6].
Structure[edit]
The aluminosilicate framework is composed of tetrahedra linked to form parallel double six-membered rings stacked in two different positions (A and B) in the repeating arrangement AABBAABB. The framework has no Al-Si order[3]. Space Group: P63/mmc. Unit Cell Parameters[2]: a=13.72 Å, c=9.95 Å, Z=4.
Environment[edit]
Generally occurs in Si-poor volcanic rocks, marine basalts and breccias, associated with other sodium zeolites such as analcime,
Na(Si2Al)O6.H2O, natrolite, Na2(Si3Al2)O10.2H2O, and chabazite-Na, Na2Ca(Si8Al4)O24.12H2O. It also occurs in Na-rich pegmatites in alkaline rocks, and as an alteration product in some nepheline syenite intrusions[6]. No sedimentary gmelinite has been found
[3]. It is generally assumed that it forms at low temperatures, less than 100 °C[6]. It is widespread as a hydrothermal alteration product of ussingite, Na2AlSi3O8(OH), associated with gobbinsite, Na5(Si11Al5)O32.11H2O, gonnardite, (Na,Ca)2(Si,Al)5O10.3H2O, and chabazite-K[6].
Notable Localities[edit]
Gmelinite-Na occurs extremely rarely at the Francon Quarry, Montreal, Canada, in sills of the igneous volcanic rock phonolite which are rich in dawsonite, NaAl(CO3)(OH)2 [7]. It occurs both as pure gmelinite-Na and interlayered with chabazite in water-quenched basalts in Western Tasmania [8]. Associated minerals include other zeolites, especially chabazite, quartz, aragonite and calcite.
Distribution[edit]
Type Locality: Monte Nero, San Pietro, Montecchio Maggiore, Vicenza Province, Veneto, Italy. Also found in Australia, Canada, Czech Republic, Germany, Hungary, Japan, Russia, UK and USA[5].
References[edit]
- ^ http://rruff.info/ima
- ^ a b c Roberts, Campbell and Rapp (1990) Encyclopedia of Minerals, 2nd edition
- ^ a b c Gaines et al (1997) Dana's New Mineralogy Eighth Edition
- ^ http://www.webmineral.com/data/Gmelinite-Na.shtml
- ^ a b http://www.mindat.org/min-6973.html Mindat.org
- ^ a b c d e Deer, Howie and Zussman (2004) Rock-Forming Minerals Volume 4B:690-696
- ^ Tarassoff, Peter, and Horvath, Lazlo and Elsa (2006) Mineralogical Record 37-1:35
- ^ Sutherland, F L and Bottrill, R S (2004) Zeolites of Western Tasmania, Australian Journal of Mineralogy 10-2: 59 - 72
External links[edit]
Category:Minerals Category:Silicate minerals Category:Tectosilicates Category:Zeolites