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Water in rocks

The augen gneiss cube contains 0.7% water by weight (70 ml).
Photo by Chip Clark. Click to zoom.
SpecimenCatalog NumberLocality
Augen gneissNMNH 116619-2Colorado, United States
GraniteNMNH 116619-15Jack Pine Mine, Colorado, United States
SandstoneNMNH 116619-20Utah, United States
Pyritic slateNMNH 116626-6Vermont, United States
SerpentiniteNMNH 116626-7Rochester, Vermont, United States

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.

At shallow depths, much of the water is stored in tiny pores between mineral grains. The rocks pictured here are arranged in order of increasing water content. Each contains the same amount of water as the beaker beside them.

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 deep crust and mantle, water is held primarily as pairs of hydrogen and oxygen atoms (hydroxyl groups) in the atomic structures of minerals. This illustration shows the atomic structure of amphibole, which contains 2% water.


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