The physical process where a solid phase transitions directly to a gas phase without going through a liquid phase.
The physical process where a solid phase transitions directly to a gas phase without going through a liquid phase.
A member of the chlorite group with a composition of Mg2(Al,Fe3+)3(Si3Al)O10(OH)8. The octahedral sheet of the 2:1 layer is dioctahedral, whereas the interlayer is trioctahedral; therefore this is a di,trioctahedral chlorite. It differs from cookeite in that it is essentially Li-free.
Cf., chlorite, cookeite, donbassite
A trioctahedral member of the true mica group with an approximate chemical composition of (NH4, K)(Fe1.33Mg0.71Al0.42Ti0.22)Si2.67Al1.33O10(OH)2. The characterizing feature is the NH4 (NH4 > K) in the interlayer site and the trioctahedral sheet; the composition suggests that suhailite may be described as an ammonium-rich biotite. Difficulties in separating suhailite from impurity phases, stacking disorder and a high numbers of defects prevented structural characterization. Impurity phases and volatility of NH4 limited the accuracy of the chemical analysis. Suhailite occurs in gneisses from the Betic Cordillera, Spain, and formed from primary annite during the annite to fibrolite transformation, probably at temperatures up to ~500 oC (Ruiz Cruz et al., 2009).
Cf., tobelite
A supercell exists if the unit cell contains a subunit (or subcell) whose periodicity is smaller than that of the parent lattice (Nespolo, 2019). Therefore, the supercell consists of multiple translations of the subcell. However, the supercell is more complex than the simple translations of the subcell units because of offsets in the translations of the subcell, relaxation effects in the bonding within subcells, or more complex structural changes in one or more subcells. A crystal with a supercell structure will display extra diffraction peaks (or superlattice reflections) with respect to its subcell structure. In molecular simulations, a “supercell” is created by multiple repeats of a subcell equal to the periodicity of the unit cell. Calculations are then made on the supercell, which may deform the connectivity of the atoms within the subcell(s), resulting in a change of the subcell periodicity within the supercell. This supercell minimizes the effect of nearest neighbors in adjacent cells.
Cf., unit cell
An industrial term for the fast (seconds to minutes) high-temperature heating (usually 900 – 1000°C) of porous clays or perlites to remove adsorbed water by volatilization, in addition to partial dehydroxylation (structural water) of the clay minerals present. For most clay minerals, the point where the rapid loss of structural water first occurs is often referred to as the onset of low volatile matter (LVM) characteristics. Termination of heating at this or a somewhat higher temperature commonly generates a material (e.g., calcium hydroxide) whose porous bulk fabric remains intact and which does not readily slake in water. Unlike calcination, which implies a complete dissociation reaction, superheating produces limited dehydroxylation without destroying plasticity (i.e., without destroying clay-like properties). Thus, LVM clays will still display a measurable weight loss on ignition.
Syn., flash heating,
Cf., low volatile matter (LVM); slake; calcine; loss on ignition; water, adsorbed; water, structural; water, zeolitic
A boundary, planar or near planar, between two phases. The term is often used to connote planar or near planar interfaces between a condensed phase (solid) and gases, liquids, or other solids, or between any two phases (e.g., liquid-liquid, gas-gas, liquid-gas). Surfaces generally have an interfacial energy term and a chemical compositional gradient existing from the surface, and a discrete molecular entity or multi-component substance may exist on or at the surface. In clay science, clay surfaces include “external surfaces” where there are broken bonds at particle edges and “internal surfaces” at the junction between the layer and the interlayer. The external surfaces include the broken-bond particle edges and the terminating basal surface. Internal surfaces, although a term commonly used in clay science, may not strictly adhere to the above definition because the material (or lack of material) in the interlayer is not necessarily a “phase”, but the atomic arrangement (or its behavior) in the interlayer is sufficiently distinct from the layer that the term is useful (e,g., the discrete molecular entity or multi-component substance addressed above). Internal surfaces are readily accessible to the environment outside the particle (often owing to the small particle size) and may have characteristics consistent with the permanent layer charge of the particle and interlayer cation size and charge. Environmental characteristics, such as water activity (e.g., pH, relative humidity), solute concentration, etc., may influence the behavior of the internal surface. External surfaces are also affected by environmental characteristics, but often the broken bonds affect the characteristics/structure of the electrolyte nearest the external surface.
Cf., interlayer, layer, phase
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.