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Formula: Na2Ca2(Si9Al6)O30.8H2O
Tectosilicate (framework silicate) zeolite group
Crystal System: Orthorhombic
Specific gravity: 2.26 measured, 2.27 calculated
Hardness: 5
Streak: White
Colour: Colourless, white, gray, yellowish
Common impurities: K
Environments
Hydrothermal environments
Basaltic cavities
Mesolite commonly occurs in cavities in volcanic rocks, typically basalt,
also in andesite, porphyry (rock with coarse phenocrysts in a finer
groundmass) and hydrothermal veins. In basaltic cavities it is generally in association with other
zeolites.
Localities
At the Marron Volcanics of the Olalla Area South-Central British Columbia, Canada, the most aesthetic mesolite
specimens are found at Yellow Lake, as rich pink to maroon acicular crystal bundles to 1.5 cm nestled on chisel-shaped
thomsonite. The red colouring is caused by
hematite inclusions. The mesolite commonly occurs in filled amygdules
where scolecite-mesolite needles have overgrown a
thomsonite lining. In some cases, calcite,
heulandite and/or analcime fill the
central part, after the scolecite-mesolite.
Colourless mesolite on pink chabazite covered in
analcime was noted in a few cavities at the Apex ski area road site
(R&M 96.6.523).
The Quarry at Pithampur, Dhar district, Madhya Pradesh state, India has produced a small number of specimens
with equant
pink-red calcite crystals to which white sprays of mesolite
are lightly attached
(Minrec 55.1.89).
In the vicinity of Meshkinshahr, Ardabil Province, Iran, mesolite is the most common
zeolite, almost always associated with
thomsonite and analcime.
In basaltic cavities in Oregon, USA, mesolite is associated with calcite,
chabazite, analcime and
stilbite
(DHZ 4 p375).
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