Epistilbite

minerals

mordenite

zeolite

laumontite

Images

Formula: Ca₃[Si₁₈Al₆O₄₈].16H₂O
Tectosilicate (framework silicate), zeolite group
Crystal System: Monocliic
Specific gravity: 2.22 to 2.28 measured, 2.266 calculated
Hardness: 4 to 4½
Streak: White
Colour: Colourless, white, orange, red
Common impurities: Fe,Mg,Na,K
Environments:

Metamorphic environments
Basaltic cavities

Epistilbite occurs in cavities in silica-rich basalt and olivine basalt, associated with laumontite, heulandite and mordenite (DHZ 4 p385). It also occurs in gneiss. No diagenetic epistilbite has been reported.

In Iceland epistilbite occurs in geothermal wells in basalt at 80 to 160^oC (Dana).

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