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Gmelinite

Zeolite mineral series

Field	Value
name	Gmelinite
category	Tectosilicate minerals
group	Zeolite group
image	Gmelinite-Na-Chabazite-Ca-153544.jpg
imagesize	260px
formula
IMAsymbol	Gmelinite-Na: Gme-Na
molweight	2,000.77 g
strunz	9.GD.05 (10 ed)
8/J.26-50 (8 ed)
dana	77.1.2.6
system	Hexagonal
class	Dihexagonal dipyramidal (6mmm)
H-M symbol: (6/m 2/m 2/m)
symmetry	P63/mmc
unit cell	a = 13.78, c = 10.03 [Å]; Z = 4
color	Colorless, white, yellow, orange, pale green, pink, red, brown and grey
habit	Hexagonal plates, or short prisms, showing hexagonal dipyramids, pyramids and basal pinacoid. {100}, {101} and {0001} dominant. May also be tabular or rhombohedral. Crystals are striated parallel to (0001)
twinning	Interpenetrant twins commonRoberts, Campbell and Rapp (1990) Encyclopedia of Minerals, 2nd edition
</ref> on {101}. The twins consist of four individuals, three are at 90° to the other and at 60° to each other<ref name	Dana/
cleavage	Good on {100}
fracture	Conchoidal
tenacity	Brittle
mohs
luster	Dull to vitreous
refractive	nω = 1.476 - 1.494, nε = 1.474 - 1.480
opticalprop	Uniaxial (-)
birefringence	δ = 0.002 - 0.014
streak	White
gravity	2.04 to 2.17
solubility	Soluble in cold 10% HCl.
diaphaneity	Transparent, translucent or opaque
other	Piezoelectric. Barely detectable radioactivity. As with all zeolites, water is released on heating, and almost all has been expelled by 400 °C.
references

8/J.26-50 (8 ed) H-M symbol: (6/m 2/m 2/m) on {101}. The twins consist of four individuals, three are at 90° to the other and at 60° to each other

Gmelinite is a series of rare zeolite minerals. The most common member is gmelinite-Na; others are gmelinite-Ca and gmelinite-K. 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.

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, , natrolite, , and chabazite-Na, . It also occurs in Na-rich pegmatites in alkaline rocks, and as an alteration product in some nepheline syenite intrusions. It is generally assumed that it forms at low temperatures, less than 100 °C. It is widespread as a hydrothermal alteration 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 which are rich in dawsonite, . 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 US.

References

"IMA Mineral List with Database of Mineral Properties".
Warr, L.N.. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine.
"Gmelinite-Na Mineral Data".
http://www.mindat.org/min-6973.html Mindat.org
Deer, Howie and Zussman (2004) Rock-Forming Minerals Volume 4B:690-696
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
No [[sedimentary]] gmelinite has been found.Gaines et al (1997) Dana's New Mineralogy Eighth Edition
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

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sodium-minerals calcium-minerals aluminium-minerals zeolite-group hexagonal-minerals minerals-in-space-group-194 minerals-described-in-1825

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