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

A binuclear complex refers an entity of atoms (i.e., a complex or more appropriately, a molecular entity or coordination entity) with two central ions (by extension, a mononuclear complex has one central ion, a trinuclear complex has three, and polynuclear complexes have more than three). The central ion is a metal ion and an electron acceptor, with ligands as electron donors. If surface sites are involved, binuclear refers to a ligand (L) binding to two metal (M) surface sites; if a ligand is bound to only one site, the adsorption complex is termed mononuclear. See figure below.

Figure 1. Illustration of mononuclear and binuclear (inner-sphere)
complexes of adsorbed metal ions on a surface.
From Maurice (2009), with permission.

See binuclear complex.

A process whereby an element or compound is incorporated into or concentrated on the surface of an organism, possibly transformed into another compound, and retained. The concentration of the element(s) or compound(s) in the biota may be greater than its concentration in the media from which it was derived. The process is of particular concern for toxins, pesticides, etc.

A microbial community generally supported by a surface and held together by extracellular attachment features such as exopolysaccharides (EPS) in a distinct 3-dimensional shape or architecture. Biofilm matrix may also include abiotic components, such as clay or other mineral particles, corrosion products, etc. that may act as support and/or as sources of nutrients.

A biological process that produces either a chemical or physical breakdown of minerals or rocks.
See weathering, physical weathering, chemical weathering

A biomineralization process where the cellular activities of an organism directly control mineral nucleation and growth, the location of nucleation, and mineral morphology. The process may be extracellular, intercellular, or intracellular. Traditional definitions of minerals preclude a biological-process origin of minerals, but such definitions are being challenged, see the definition of “mineral” for a more classic approach.
Cf., mineral, biologically induced mineralization, biomineralization

A biomineralizaton process where solution conditions and/or surfaces for heterogeneous nucleation are altered by the cell to promote mineralization. However, the cell does not directly control the type of mineral formed or habit. Traditional definitions of minerals preclude a biological-process origin of minerals, but such definitions are being challenged, see the definition of “mineral” for a more classic approach.
Cf., biomineralization, biologically controlled mineralization, mineral,