basaltic cavities

The phillipsite group is a group of tectosilicates (framework silicates) and a sub-group of the zeolite group, comprising:
Phillipsite-Ca: Ca3(Si10Al6)O32.12H2O
Phillipsite-K: K6(Si10Al6)O32.12H2O
Phillipsite-Na: Na6(Si10Al6)O32.12H2O
Phillipsite forms a series with harmotome
Specific gravity: 2.2
Hardness: 4 to 5
Streak: White
Colour: White
Solubility: Moderately soluble in hydrochloric acid

Sedimentary environments
Hydrothermal environments
Basaltic cavities (most commonly)

Phillipsite is a common zeolite in basaltic cavities, ore veins, lithified rhyolitic vitric tuff (consolidated pyroclastic rock), saline lake deposits, and ocean floor sediments. It forms in Iceland in geothermal wells at 60 to 85oC
Phillipsite is a mineral of the zeolite facies

In the basaltic rocks near Kladno, Czechoslovakia, phillipsite is associated with thomsonite, mesolite, chabazite and natrolite, and it is always the first of these minerals to have been formed.

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