See reyerite group.

See alkali feldspar.

A pyroxene subgroup of Mg-Fe pyroxenes in the enstatite-ferrosilite solid-solution series with orthorhombic (Pbca, Pbcn) symmetry. See pyroxene group for additional details.
Cf., enstatite

A physical process by which a solvent (typically, water) diffuses through a semi-permeable membrane (a porous material which is permeable to the solvent, but not the solute), owing to differences in solvent activity of two solutions which are separated by the membrane.

The differential pressure exerted by a solvent across a semi-permeable membrane owing to the difference in solvent activity between two solutions separated by the membrane.

Interlayer expansion that occurs in phyllosilicate minerals responding to the effects of temperature, pressure and composition (e.g., chemical potential) of an electrolyte surrounding the mineral with respect to the interlayer H₂O (i.e., the “osmotic effect” or “osmotic pressure”). At equilibrium, the chemical potential of H₂O in the electrolyte and in the interlayer is related to the salt concentration of the electrolyte (the osmotic pressure is zero). At a given temperature, pressure, or composition away from equilibrium, there will be a difference in chemical potential between the electrolyte and clay interlayer and the resulting osmotic pressure will be the driving force to affect the layer-to-layer distance. Under certain conditions, the resulting osmotic pressure drives the clay layers further apart than the interlayer distances common to intracrystalline swelling.
Cf., intracrystalline swelling

A recrystallization process where the smallest crystals dissolve and the chemical constituents are added to the larger crystals of the same phase. This process of crystal growth and coarsening occurs in a solution. The driving mechanism is a shift to lower surface free energy (Ostwald, 1900 in Baronnet, 1982).

Defined by Schultz (1969) for montmorillonite samples [current nomenclature for montmorillonite is that it is an Al-rich, dioctahedral smectite with an ideal structural formula of (Al_3.15Mg_0.85)Si₈O₂₀(OH)₄X_0.85.nH₂O with layer charge from primarily octahedral substitutions of Mg] with a large net negative layer charge [-0.80 to -1.20 per unit cell, O₂₀(OH)₄] obtained almost entirely (<0.15 charge from tetrahedral sheet) from cation substitutions in the octahedral sheet, although exceptions were noted. This classification scheme was based on chemical and thermal analysis. The term is obsolete and should not be used. Terms used in this obsolete classification are: Wyoming-type, Otay-type, Chambers-type, Tatatila-type, beidellite-type (ideal and non-ideal), and non-ideal montmorillonite. See also Part 2 of the Glossary.

Ions adsorbing in the outer Helmholtz plane form outer sphere complexes. The larger distance to the surface relative to the shorter distances of inner sphere complexes may result from retaining H₂O molecules (via hydration) between the surface and the ion.

In mining, overburden refers to the unusable material(s) that is above the ore of interest. Overburden may be removed or left in place (by tunneling below it).