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

An obsolete varietal term for biotite.

See pyroxenoid group.

A trioctahedral mica that shows interlayer deficiency. It is a series name (Rieder et al., 1998) with a generalized composition of Na_0.5v_0.5Mg_2.5Al_0.5(AlSi₃)O₁₀(OH)₂, where = vacancy The formula indicates that it is not an end-member composition. Series names designate that additional research may be warranted.