1. n. [Geology]

Incorporation of water into the atomic structure of a mineral, i.e., the chemical combination of water and another substance. Gypsum is a hydrate mineral. Its anhydrous equivalent is anhydrite.

See related terms: gypsum,  hydrate,  mineral

2. n. [Drilling Fluids]

Absorption of water by a hygroscopic material such as a clay or polymer. Hydration is the first stage of clay-water (or polymer-water) interaction. When dry bentonite is stirred into water, hydration is observed as swelling.

See related terms: clay-water interaction,  colloid,  hardness ion,  hydrate,  hydrophilic,  inhibit,  inhibitive mud,  montmorillonite,  prehydrated bentonite,  prehydration,  seawater mud,  soft water,  XC polymer