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Formula: NaCa4(Si27Al9)O72
.28H2O
Tectosilicate (framework silicate), stilbite subgroup of the
zeolite group
Crystal System: Monoclinic (pseudo orthorhombic)
Specific gravity: 2.19 measured, 2.23 calculated
Hardness: 3½ to 4
Streak: White
Colour: White, red, yellow, brown, cream
Luminescence: May fluoresce pale-yellow or blue-white in short wave UV
Solubility: Moderately soluble in hydrochloric acid
Environments:
Metamorphic environments
Basaltic cavities
Stilbite-(Ca) is a low-temperature hydrothermal mineral occurring in amygdaloidal cavities in
basalts, andesites, and
various metamorphic rocks. Formed in hot springs deposits, and as a cementing agent in some
sandstones and
conglomerates. Associated minerals include
zeolites, prehnite,
calcite and quartz
(HOM).
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