There are two kinds of surface complexes, one with no H2O molecules interposed between it and the mineral surface, termed an inner-sphere complex, and one in which at least one H2O molecule is interposed, and this is termed an outer-sphere complex (Sposito, 1989). Inner-sphere complexes are chemically bonded; outer-sphere complexes or those that exist in the diffuse layer are said to by physically adsorbed (Parks, 1990).
‘surface controlled’ growth or dissolution requires the rate-determining step in the growth or dissolution reaction to occur at the mineral surface; this rate-determining step is in the form of an attachment to or a detachment from the surface of a metal or metal-ligand ‘activated complex.’
A wetting agent that lowers the surface tension of a liquid or lowers the interfacial tension between two liquids. Detergents are an important economic group of wetting agents that can affect clay surfaces.
A two-phase system with a solid (“dispersed phase”) dispersed in a fluid (“continuous phase”). In colloid chemistry, a suspension differs from a colloidal suspension (or “sol”) by having particles >1μm. The term “suspension” is preferred over “clay solution” or “colloidal solution” to avoid confusion with true solutions, which do not have an interface. Thus, the presence of an interface between the solid and the liquid phase (in the thermodynamic sense) is important. The table below lists names for systems with dispersed phases.
See blunging.
See astrophyllite group.
An obsolete varietal term for celadonite.
See corrensite and chlorite/smectite.
A clay that can sorb large amounts of water and thereby expands in volume. The swelling clay minerals, smectite and vermiculite, if they occur as fine-grained material, are referred to as “swelling clays”. In industry, bentonites are commonly referred to as “swelling clay”. Some clays that are referred to as “swelling clays” have been shown to be dominated by clay minerals characterized by interstratifications of two varieties of phyllosilicate layers, one being expandable via adsorption of H2O and one not, as in “swelling chlorite” which is interstratified chlorite and smectite.
Syn., expandable clay
Cf., swelling clay mineral
A clay mineral that can sorb large amounts of water and thereby expands in volume. Both vermiculite and smectite are swelling clay minerals.
Cf., swelling clay.
Swinefordite is the Mg- and Li-rich trioctahedral member of the smectite group, with the original workers (Tien et al., 1975) determining that the location of Li of the natural sample was split with ~33% in the interlayer and the remainder in the octahedral sheet, and with vacancies in the octahedral site, thereby making this a dioctahedral-trioctahedral intermediate. Köster (1982) redetermined the chemistry based on the cation exchange capacity and determined the composition to be (M+0.4 . nH2O)(Li1.06Al0.99 Mg0.7Fe3+0.10)Σ=2.85 (Si3.87Al0.13)O10(OH)2 where M is the exchangeable cation and n is variable. The M (interlayer) cation is assumed here as univalent, but it may have other valence states also. The vacancy content in the octahedral site (0.15) is consistent with other trioctahedral smectites (Güven, 1988). Swinefordite occurs as a pseudomorph after spodumene.
Cf., hectorite