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Formula: (Ca,Na,K)5(Si27Al9)O72.26H2O
Tectosilicate (framework silicate), heulandite subgroup,
zeolite group, forms a series with
clinoptilolite-Ca
Crystal System: Monoclinic
Specific gravity: 2.1 to 2.2 measured, 2.17 calculated
Hardness: 3½ to 4
Streak: White
Colour: White, colorless, red, yellow, brown, green
Environments
Heulandite-Ca occurs in cavities in basalt and as a
devitrification product from volcanic glasses
Localities
The type locality is Strathclyde, Scotland, UK.
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