Chalcedony is a rock term to describe a mixture of a fibrous [112̅ 0] variety of microcrystalline (length fast) quartz and moganite.
Cf., quartzine

An obsolete varietal term for stilpnomelane.

See birnessite.

A now-obsolete term first used by Schultz (1969) to define montmorillonite samples on the basis of chemical and thermal analysis with a total net layer charge of -0.85 to -1.20 per unit cell [O₂₀(OH)₄], with a layer-charge contribution from tetrahedral substitutions of between -0.15 to -0.50, although exceptions were noted. See Tatatila- type montmorillonite. 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. 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.
See also Part 2 of the Glossary.

The Fe-rich member of the chlorite group with a composition of ideally Fe²⁺₅Al(Si₃Al)O₁₀(OH)₈. There may be considerable substitutions of Mg, Fe³⁺, and Al for Fe²⁺. The common polytype is the IIb form, a one-layer form. Chamosite is an important constituent in oolitic and sedimentary iron formations and may be found as grain coatings in sandstones.
See chlorite

A ceramic raw material with a high silica and alumina composition typically produced by firing selected “fire clays” to high temperatures before grinding and screening to specific particle sizes. Chamotte is usually porous with a low bulk density.
Cf., fire clay

The state in which the rates of forward and reverse reactions are equal; thus, at equilibrium, the change in free energy ΔG = 0.

The study of reaction rates and mechanisms.

A thermodynamic term for the change of the Gibbs free energy of a system with respect to the change in the number of moles of a specific constituent. Chemical potential is equivalent to partial molar enthalpy, partial molar free energy, partial molar internal energy, and partial molar Helmholtz function. The chemical potential may be described as a force of energy change caused by a change of composition.

See thermodynamics.