Gmelinite-Na is one of the rarer

zeolites Zeolites are microporous, crystalline aluminosilicate materials commonly used as commercial adsorbents and catalysts. They mainly consist of silicon, aluminium, oxygen, and have the general formula ･y where is either a metal ion or H+. These pos ...

but the most common member of the gmelinite series, gmelinite-Ca, gmelinite-K and gmelinite-Na. It is closely related to the very similar mineral

chabazite Chabazite ()The New Oxford Dictionary of English (1998) - p. 300 "chabazite /'kabəzʌɪt/ noun "A colourless, pink or yellow zeolite mineral, typically occurring as rhombohedral crystals.". is a tectosilicate mineral of the zeolite group, close ...

. Gmelinite was named as a single species in 1825 after

Christian Gottlob Gmelin Christian Gottlob Gmelin (12 October 1792 – 13 May 1860) was a German chemist. He was born in Tübingen, Germany, and was a grandson of Johann Konrad Gmelin and a great-grandson of Johann Georg Gmelin. Scientific career In 1818, Gmelin was one ...

(1792–1860) professor of chemistry and mineralogist from

Tübingen Tübingen (, , Swabian: ''Dibenga'') is a traditional university city in central Baden-Württemberg, Germany. It is situated south of the state capital, Stuttgart, and developed on both sides of the Neckar and Ammer rivers. about one in thr ...

, Germany, and in 1997 it was raised to the status of a series.Deer, Howie and Zussman (2004) Rock-Forming Minerals Volume 4B:690-696
Gmelinite-Na has been synthesised from Na-bearing

aluminosilicate Aluminosilicate minerals ( IMA symbol: Als) are minerals composed of aluminium, silicon, and oxygen, plus countercations. They are a major component of kaolin and other clay minerals. Andalusite, kyanite, and sillimanite are naturally occurr ...

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 In geometry, a tetrahedron (plural: tetrahedra or tetrahedrons), also known as a triangular pyramid, is a polyhedron composed of four triangular faces, six straight edges, and four vertex corners. The tetrahedron is the simplest of all the o ...

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.Senderov and Shishakova (1967) Russian Chemical Bulletin 16-1:151 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 Volcanic rock (often shortened to volcanics in scientific contexts) is a Rock (geology), rock formed from lava erupted from a volcano. In other words, it differs from other igneous rock by being of Volcano, volcanic origin. Like all rock types, ...

, marine

basalts Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% of a ...

and

breccias Breccia () is a rock composed of large angular broken fragments of minerals or rocks cemented together by a fine-grained matrix. The word has its origins in the Italian language, in which it means "rubble". A breccia may have a variety of d ...

, associated with other sodium zeolites such as

analcime Analcime (; ) or analcite is a white, gray, or colorless tectosilicate mineral. Analcime consists of hydrated sodium aluminium silicate in cubic crystalline form. Its chemical formula is Na Al Si2 O6· H2O. Minor amounts of potassium and calciu ...

, ,

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. It was named natrolite by Martin Heinrich Klapro ...

, , and chabazite-Na, . It also occurs in Na-rich

pegmatites A pegmatite is an igneous rock showing a very coarse texture, with large interlocking crystals usually greater in size than and sometimes greater than . Most pegmatites are composed of quartz, feldspar, and mica, having a similar silicic co ...

in alkaline rocks, and as an alteration product in some

nepheline syenite Nepheline 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 al ...

intrusions. No

sedimentary Sedimentary rocks are types of rock (geology), rock that are formed by the accumulation or deposition of mineral or organic matter, organic particles at Earth#Surface, Earth's surface, followed by cementation (geology), cementation. Sedimentati ...

gmelinite has been found.Gaines et al (1997) Dana's New Mineralogy Eighth Edition It is generally assumed that it forms at low temperatures, less than 100 °C. It is widespread as a

hydrothermal alteration Metasomatism (from the Greek μετά ''metá'' "change" and σῶμα ''sôma'' "body") is the chemical alteration of a rock by hydrothermal and other fluids. It is the replacement of one rock by another of different mineralogical and chemical com ...

product of ussingite, , associated with gobbinsite, , gonnardite, , and chabazite-K.

Notable localities

Gmelinite-Na occurs extremely rarely at the Francon Quarry, Montreal, Canada, in sills of the igneous volcanic rock

phonolite Phonolite is an uncommon extrusive rock, of intermediate chemical composition between felsic and mafic, with texture ranging from aphanitic (fine-grained) to porphyritic (mixed fine- and coarse-grained). Phonolite is a variation of the igneous ...

which are rich in

dawsonite Dawsonite is a mineral composed of sodium aluminium carbonate hydroxide, chemical formula NaAlCO3(OH)2. It crystallizes in the orthorhombic crystal system. It is not mined for ore. It was discovered in 1874 during the construction of the Redpath ...

, .Tarassoff, Peter, and Horvath, Lazlo and Elsa (2006) Mineralogical Record 37-1:35 It occurs both as pure gmelinite-Na and interlayered with

in water-quenched basalts in Western Tasmania.Sutherland, F L and Bottrill, R S (2004) Zeolites of Western Tasmania, Australian Journal of Mineralogy 10-2: 59 - 72 Associated minerals include other zeolites, especially chabazite,

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical form ...

aragonite Aragonite is a carbonate mineral, one of the three most common naturally occurring crystal forms of calcium carbonate, (the other forms being the minerals calcite and vaterite). It is formed by biological and physical processes, including prec ...

and

calcite Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...

Distribution

Type Locality: Monte Nero, San Pietro,

Montecchio Maggiore Montecchio Maggiore ( vec, Montécio Majore) is a town and ''comune'' in the province of Vicenza, Veneto, Italy. It is situated approximately west of Vicenza and east of Verona; SP 246 provincial road passes through it. Montecchio Maggiore bord ...

, Vicenza Province, Veneto, Italy. Also found in Australia, Canada, Czech Republic, Germany, Hungary, Japan, Russia, UK and US.

References

External links

Structure type GME
{{Commons Sodium minerals Calcium minerals Aluminium minerals Zeolites Hexagonal minerals Minerals in space group 194