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TITLE: All Rocks Contain Water

You can’t necessarily sip it with a straw, but water is a component of most rocks. Both at and below Earth’s surface, water in rocks drives geological processes. Within Earth, water plays a critical role in transforming and melting rocks. Where is the water in rocks? At shallow depths, much of the water is stored in tiny pores between mineral grains. Throughout the crust and mantle, water is held primarily as pairs of hydrogen and oxygen atoms (hydroxyl groups) in the atomic structures of minerals.

[Photo: Augen Gneiss with beaker showing water level.]

Augen Gneiss
Contains 0.7% water by weight.


[Photo: Sandstone with beaker showing water level.]

Contains 1.6% water by weight.


[Photo: Serpentinite with beaker showing water level.]

Contains 12.5% water by weight.


[Photo: Granite with beaker showing water level.]

Contains 0.8% water by weight.


[Photo: Pyrite bearing Phylite with beaker showing water level.]

Pyrite bearing Phylite
Contains 6.9% water by weight.

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Smithsonian National Museum of Natural History Department of Mineral Sciences website Credits