User:Strickja/Gmelinite-Na

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. Gmelinite-Na has been synthesised from Na-bearing aluminosilicate gels.

Structure
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. Space Group: P63/mmc. Unit Cell Parameters : a=13.72 Å, c=9.95 Å, Z=4.

Environment
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. No sedimentary gmelinite has been found . It is generally assumed that it forms at low temperatures, less than 100 °C. 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.

Notable Localities
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 . It occurs both as pure gmelinite-Na and interlayered with chabazite in water-quenched basalts in Western Tasmania . Associated minerals include other zeolites, especially chabazite, quartz, aragonite and calcite.

Distribution
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.