Water (more precisely, H₂O or OH molecules) that is directly bound to cations at crystallographic sites in a crystal structure. This H₂O or OH is capable of being driven off at elevated temperature, generally by heating to 1000^oC. For phyllosilicates, structurally bound “water” is in the form of hydroxyl (OH) groups coordinated to cations, and the high temperature is required to promote dehydroxylation. Fluorine and certain other anions may be driven off at these temperatures also. However, hydrates, such as gypsum (CaSO₄ .2H₂O), have structural water coordinated to cations as H₂O (e.g., water of hydration) that is liberated by heating to relatively low values, 65 – 95^oC.
Syn. combined water, molecular water, structurally bound water, water of crystallization, water of hydration. “Lattice water” is also used, but is not recommended because a “lattice” refers to a collection of identipoints, see “lattice”.
Cf., water, adsorbed

Water molecules adsorbed within the cavities/tunnels of the zeolite framework structure, commonly removed by heating at 350 to 400^oC for about 12 hours. “Zeolitic water” was a term used by early workers to describe interlayer water of phyllosilicates. However, the analogy is imperfect (and not in use anymore) because the number of interlayer water molecules affects the layer-to-layer spacing of a phyllosilicate, whereas the shape and size of zeolitic tunnels are not significantly affected by the number of H₂O molecules present.
Cf., water, structural; water, adsorbed

The physical (mechanical) and/or chemical breakdown of rock, sediment, and soil in place under the influence of the hydrosphere and/or atmosphere. Biota may influence or control physical or chemical weathering.
See physical weathering, chemical weathering.
Cf., erosion

See hydrotalcite group.

An industrial or commercial term, originally used to designate the high quality sodium bentonite from Wyoming, USA. This material exhibits characteristics of high water adsorption, dilation, viscosification and dry sand binding strength. Usage of the term has since broadened to include any bentonite having performance characteristics equal to that of high quality sodium bentonite from Wyoming. Whereas the term “Western Bentonite”, and its synonyms, continue to have meaning in the industrial and commercial realm, they are scientifically obsolete and should not be used in that context.
Syn: Wyoming Bentonite, Wyoming Sodium Bentonite, Wyoming-Type Bentonite

A field term used to describe a light-colored, mica, usually in metamorphic rocks, such as muscovite and margarite, and also illite, phengite, and celadonite.

Any ceramic that fires to a white or ivory color, commonly used in wall tiles, tableware, etc.

Willemseite is the Ni-rich (Ni > Mg) member of the talc group. Willemseite occurs at Barberton Mountain Land, Transvaal.

An obsolete local, varietal term for antigorite serpentine of various colors, but typically green, from West Chester, Chester County, Pennsylvania, USA.

A member of the palygorskite-sepiolite group with a composition of approximately (Ca_1.68Mn_0.32)Fe³⁺_2.96(Si_7.87 Al_0.08)O₂₀(OH)₄^. 10H_1.98O.
See palygorskite-sepiolite group