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Formula:
Clinoptilolite-Ca: Ca3(Si30Al6)O72.20H2O
Clinoptilolite-K: K6(Si30Al6)O72.20H2O
Clinoptilolite-Na: Na6(Si30Al6)O72.20H2O
All are tectosilicates (framework silicates), zeolite group
Specific gravity: 2.1 to 2.2
Hardness: 3½ to 4
Streak: White
Colour: White, Reddish white, red
Environments:
Volcanic igneous environments
Basaltic cavities
Clinoptilolite is most commonly formed as a devitrification product of silicic volcanic glass from
tuff. It also
occurs in cavities in rhyolite, andesite, and
basalt. Associated minerals include other zeolites,
montmorillonite, hectorite,
thénardite, halite,
gaylussite, celadonite,
quartz, opal and
calcite
(Dana, HOM).
Clinoptilolite is very similar to heulandite, but the response to temperature is different for
the two minerals; clinoptilolite has a high heat resistance such that heating at 750oC does not normally destroy the lattice,
whereas the heulandite lattice is destroyed
at a much lower temperature of about 550oC
(AM 57.1448-1462).
Localities
At the Cañadón Hondo, Neuquén Province, Argentina, clinoptilolite occurs as a layer 6-8 cm thick interbedded with
bentonitic
clay. A specimen has been found with one surface coated with a 1 mm layer of
baryte. The clinoptilolite apparently was formed by the alteration of
fine-grained volcanic glass;
it has rare thin veinlets of opal and
montmorillonite. The
bentonitic clay consists essentially of
montmorillonite
(AM 45.341-345).
At the Hector Bentonite Mine No. 1, Hector, Cady Mountains, San Bernardino county, California, USA,
clinoptiloloite has been found in beds of
altered pyroclastic material, closely associated with montmorillonite
and hectorite
(AM 45.351-369).
At the SK Star #2 Mining Claim, The Cove, Topaz Mountain, Thomas Range, Juab County, Utah, USA, a few areas have
produced clinoptilolite-(Na) with a purple hue. The matrix is highly fluorescent green under short wave UV light and
mildly fluorescent under long wave UV light
(MinRec 51.6.809-810).
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