Mineral description : Heulandite

Heulandite from India.

Mineral class	Silicates : Tekto silicates : Zeolites
Chemical formula	Ca[Al2Si7O18]*6H2O (Mineraler, stenar och ädelstenar) CaNa2[Al2Si3O8]2*5H2O (Mineraler och bergarter) (Na,Ca)2-3Al3(Al,Si)2Si13O36*12H2O (Norsk steinbok) (Bergarter, mineral, fossil) (There seems to be some difference between books about the chemical formula)
Crystal system	Tricline, pseudo monocline.
Habitus	Crystals tabular or pseudoortorombic.
Cleavage	One complete cleavage. Uneven fracture.
Hardness	3.5-4
Density	2.1-2.2
Color	White, pink, red or brown. Transparent to translucent.
Streak	White.
Luster	Glas, pearly on cleavages.
Description
Occurance	In cavities in basaltic rocks or in secondary sedimentary rocks.
Associates	Stilbite.
Notes	All zeolites are soluble in strong hydrocloric acid when powdered, leaves silicagel as a rest. The water is driven out when heated. Melted by a micro flame.
Locations	Not found in Sweden. India.

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