Gmelinite
Encyclopedia
Gmelinite-Na is one of the rarer zeolites but the commonest member of the gmelinite series, gmelinite-Ca, gmelinite-K and gmelinite-Na. It is closely related to the very similar mineral chabazite
. Gmelinite was named as a single species in 1825 after Christian Gottlob Gmelin (1792–1860) professor of chemistry and mineralogist from Tübingen
, Germany, and in 1997 it was raised to the status of a series.
Gmelinite-Na has been synthesised from Na-bearing aluminosilicate
gels. The naturally occurring mineral forms striking crystals, shallow, six sided double pyramids, which can be colorless, white, pale yellow, greenish, orange, pink, and red. They have been compared to an angular flying saucer.
, c=9.95 Å, Z=4.
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.
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
.
, Vicenza Province, Veneto, Italy. Also found in Australia, Canada, Czech Republic, Germany, Hungary, Japan, Russia, UK and USA.
Chabazite
Chabazite is a tectosilicate mineral of the zeolite group, closely related to gmelinite, with formula Al2Si4O12·6H2O. Recognized varieties include Chabazite-Ca, Chabazite-K, Chabazite-Na, and Chabazite-Sr, depending on the prominence of the indicated cation.Chabazite crystallizes in the triclinic...
. Gmelinite was named as a single species in 1825 after Christian Gottlob Gmelin (1792–1860) professor of chemistry and mineralogist from Tübingen
Tübingen
Tübingen is a traditional university town in central Baden-Württemberg, Germany. It is situated south of the state capital, Stuttgart, on a ridge between the Neckar and Ammer rivers.-Geography:...
, Germany, and in 1997 it was raised to the status of a series.
Gmelinite-Na has been synthesised from Na-bearing aluminosilicate
Aluminosilicate
Aluminosilicate minerals are minerals composed of aluminium, silicon, and oxygen, plus countercations. They are a major component of kaolin and other clay minerals....
gels. The naturally occurring mineral forms striking crystals, shallow, six sided double pyramids, which can be colorless, white, pale yellow, greenish, orange, pink, and red. They have been compared to an angular flying saucer.
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. Within the structure there are cavities with a cross-section of up to 4 Å, and also wide channels parallel to the c axis with a diameter of 6.4 Å. Space group: P63/mmc. Unit cell parameters: a=13.72 ÅÅngström
The angstrom or ångström, is a unit of length equal to 1/10,000,000,000 of a meter . Its symbol is the Swedish letter 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
Natrolite
Natrolite is a tectosilicate mineral species belonging to the zeolite group. It is a hydrated sodium and aluminium silicate with the formula . The type locality is Hohentwiel, Hegau, Germany....
, 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
Nepheline syenite
Nephelene syenite is a holocrystalline plutonic rock that consists largely of nepheline and alkali feldspar. The rocks are mostly pale colored, grey or pink, and in general appearance they are not unlike granites, but dark green varieties are also known...
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
Ussingite
Ussingite is a silicate mineral with formula Na2AlSi3O8.It was named for Niels Viggo Ussing , Copenhagen, Denmark....
, 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 phonolitePhonolite
Phonolite is a rare igneous, volcanic rock of intermediate composition, with aphanitic to porphyritic texture....
which are rich in dawsonite
Dawsonite
Dawsonite is a mineral composed of sodium aluminium carbonate hydroxide, chemical formula NaAlCO32. It crystallizes in the orthorhombic crystal system. It is not mined for ore. It was discovered in 1874 during the construction of the Redpath Museum in a feldspathic dike on the campus of McGill...
, NaAl(CO3)(OH)2.
It occurs both as pure gmelinite-Na and interlayered with chabazite
Chabazite
Chabazite is a tectosilicate mineral of the zeolite group, closely related to gmelinite, with formula Al2Si4O12·6H2O. Recognized varieties include Chabazite-Ca, Chabazite-K, Chabazite-Na, and Chabazite-Sr, depending on the prominence of the indicated cation.Chabazite crystallizes in the triclinic...
in water-quenched basalts in Western Tasmania.
Associated minerals include other zeolites, especially chabazite, quartz
Quartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
, aragonite
Aragonite
Aragonite is a carbonate mineral, one of the two common, naturally occurring, crystal forms of calcium carbonate, CaCO3...
and calcite
Calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...
.
Distribution
Type Locality: Monte Nero, San Pietro, Montecchio MaggioreMontecchio Maggiore
Montecchio Maggiore is a town and comune in the province of Vicenza, Veneto, Italy. It is situated approximately 12 km west of Vicenza and 43 km east of Verona, SP 246 passes through it....
, Vicenza Province, Veneto, Italy. Also found in Australia, Canada, Czech Republic, Germany, Hungary, Japan, Russia, UK and USA.