Tobermorite

monticellite

natrolite

Formula: Ca4Si6O17(H2O)2.(Ca.3H2O) phyllosilicate
Specific gravity: 2.40 to 2.48
Hardness: 3
Streak: White
Colour: White, pinkish white
Common impurities: Al,Fe,Mg,Na,K,H2O
Environments:

Metamorphic environments
Hydrothermal environments
Basaltic cavities

Tobermorite is a hydrothermal alteration product of calcium carbonate rocks, due to contact metamorphism, and it is found filling vesicles and cavities in basalt (Webmin). Associated minerals include gyrolite, natrolite, zeolites, ettringite and calcite (Dana).

Localities

The type locality is Tobermory, Isle of Mull, Argyll and Bute, Scotland, UK.

At Crestmore, California, USA, tobermorite is associated with blue calcite, monticellite and vesuvianite (Dana).

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