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Gmelinite is the name for three minerals:
Gmelinite-Ca: Ca2(Si8Al4)O24.11H2O
Gmelinite-K: K4(Si8Al4)O24.11H2O
Gmelinite-Na4(Si8Al4)O24.11H2O
These minerals are tectosilicates (framework silicates),
zeolite group
Specific gravity: 2.04 to 2.17
Hardness: 4½
Streak: White
Colour: Colourless, white, yellow, greenish white, orange, pale green, pink, red, brown and grey
Environments:
Pegmatites
Metamorphic environments
Hot spring deposits
Hydrothermal environments
Basaltic cavities
Gmelinite generally occurs in cavities in silica-poor volcanic rocks, and also in sodium-rich
pegmatites and
55 to 75oC geothermal wells. No sedimentary gmelinite has been reported. It is a product of
diagenetic reactions, hydrothermal activity or alteration of
basalt. Common associates are other
zeolites, quartz,
aragonite and calcite
(Dana).
In the zeolite localities of Northern Ireland gmelinite is associated with chabazite,
thomsonite, analcime,
phillipsite, lévyne,
calcite and aragonite
(DHZ 4 p400).
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