Ferrierite

tectosilicate

basaltic cavities

Ferrierite comprises three minerals:
Ferrierite-K, (K,Na)5(Si31Al5)O72.18H2O
Ferrierite-Mg, [Mg2(K,Na)2Ca0.5](Si29Al7)O72.18H2O
Ferrierite-Na, (Na,K)5(Si31Al5)O72.18H2O
They are tectosilicate (framework silicates), zeolite group
Specific gravity: 2.06 to 2.23
Hardness: 3 to 3½
Streak: White
Colour: Colourless, white, pink, orange, red due to Fe3+
Environments:

Metamorphic environments
Sedimentary environments
Basaltic cavities

Ferrierite occurs in cavity fillings in basaltic rocks and as a diagenetic mineral in rhyolite tuff, as a result of hydration reactions. It also occurs in metamorphic rocks (Dana).

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