A generic industrial classification for a white- or nearly white-colored bentonite clay (primarily smectite, illite, and/or interstratifications), generally low in iron-bearing and organic phases, and often containing some kaolin and/or minor silicate accessory minerals (quartz, feldspar, opal, etc.). White bentonite is a common base material for many value-added industrial and consumer applications and products.

See “bole”, halloysite.

A member of the serpentine group with an ideal composition of approximately (Fe²⁺, Mn²⁺, Mg)_3-x(Fe³⁺, Al)_x(Si₂-xAl_x)O₅(OH)₄. Berthierine is commonly found in unmetamorphosed sedimentary iron formations. Berthierine occurs more commonly as either an apparent trigonal (possibly 1T) or less commonly as an apparent monoclinic (possibly 1M) polytype, and both polytypes are generally intergrown. Berthierine is often confused in the older literature with chamosite, a member of the chlorite group, but not to be confused with berthierite, a sulfide mineral.
Cf., brindleyite, chamosite

An obsolete term for muscovite.

A double layer of atoms or molecules. In clay science, an example would be an alkylammonium organoclay.
See bilayer, phyllosilicate for an example.
Cf., alkylammonium organoclay bilayer; bilayer, phyllosilicate; monolayer, phyllosilicate

An interlamellar arrangement of two monolayers of alkylammonium cations [each monolayer has a C-C-C plane of the alkyl chain parallel to the (001) plane of the silicate 2:1 layers] between 2:1 layers of a phyllosilicate. The positively charged end groups (e.g., –NH₄⁺) of the alkylammonium cations are attached to the interlayer silicate surfaces to produce a characteristic d value depending on the identity of the alkylammonium cation.
Cf., alkylammonium layer charge method, alkylammonium organoclay, bilayer, monolayer, organoclay

Between the 1:1 or 2:1 layers of a phyllosilicate, a bilayer is an arrangement within the interlayer of two planes of molecules. The planes are only approximate, but the spacing seem to suggest planar features. For a bilayer hydration shell, the H₂O molecules are in an octahedral coordination around a central cation, with three H₂O above and three below the cation, and the spacing appears as two H₂O planes or “layers”. The spacing is generally not affected by the cation because the cation is small and resides well within the hydration shell of H₂O. Thus, the bilayer only refers to the two planes of H₂O molecules.
Cf., alkylammonium organoclay bilayer

An obsolete term for pyrophyllite or a mixture with dominant pyrophyllite.

A solid material that holds (binds) other materials or phases together. Binders are often formed from liquid or pasty suspensions which harden upon drying, both in artificial (e.g. cement in a masonry) and natural systems (e.g. carbonate cement in sandstones). Hardening may be solely by evaporation or by precipitation of new phases (e.g., calcite).
Cf., cement, concrete, Portland cement

A site on a clay mineral surface available for electrostatic attraction between oppositely charged species, including metal coordination bonding, and anion or polar molecule attractions, etc. Binding sites commonly occur: (1) where bonds are broken at particle edges (terminal edges) leaving a net positive charge and a possible under-bonded arrangement where bond lengths adjust accordingly to approach overall charge balance. Alternatively, any anion may compensate for the broken bond, with (OH)^– most common (and thus these sites may be affected by pH). (2) to charge balance isomorphous substitutions that occur within the 2:1 or 1:1 layer, for example, cations in the interlayer of smectite compensate for the (permanent) negative layer charge on the basal plane atoms.
Cf., edge site