The state in which the rates of forward and reverse reactions are equal; thus, at equilibrium, the change in free energy ΔG = 0.
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.
The process whereby chemical reactions alter or break down minerals or rocks under the influence of meteoric water at or near the Earth’s surface. Specific chemical weathering reactions include, but are not limited to, dissolution (congruent or incongruent), oxidation, hydrolysis, cation exchange, complexation, hydration, carbonation, and sulfation. Chemical weathering may be biologically influenced.
See weathering, physical weathering
A clay treated with chemical substances to improve properties or to increase reactivity. Chemical activation includes alkaline and acid activation.
Cf., acid activated clay, alkaline activated clay
A dioctahedral member of the brittle mica group. The end-member formula is: BaV2□Al2Si2O10(OH)2, where □ = vacancy, but known samples are deficient in Ba (or K). Typical site substitutions primarily occur in the octahedral site by Al, Fe, and/or Mg. The 2M1 polytype is the common polytype. Chernykhite is only known from southern Kazakhstan.
Cf., roscoelite
Porcelain was first made in China using kaolin, feldspar, and quartz. Traders brought porcelain back to Europe and when porcelain was made in Meissen, Germany and in England, the primary kaolin used in the formulation was called “China Clay”. The term is still used today largely in Europe and is synonymous with kaolin.
A group name for phyllosilicates with the general formula of (R2+6-y-zR3+y□z) (Si4-xR3+x)O10(OH)8 where ▫ represents vacancies, x is the number of tetrahedral R3+ cations, y is the number of octahedral R3+ cations, and z is the number of vacancies. The common structure consists of negatively charged trioctahedral 2:1 layers alternating regularly with positively charged trioctahedral interlayer sheets. Ideal composition of the 2:1 layer is (R2+, R3+)3(Si4-xR3+x)O10(OH)2 and that of the interlayer is (R2+, R3+)3(OH)6. Bayliss (1975) defined trioctahedral end members based on the dominant cation, e.g., Fe-rich, chamosite; Mg-rich, clinochlore; Mn-rich, pennantite; Ni-rich, nimite; Zn-rich, baileychlore. The trioctahedral chlorites are commonlyfound in metamorphic rocks and are the diagnostic mineral of the greenschist facies. Chlorite is also a common alteration product. Eggleton and Bailey (1967) combined composition and structure characteristics to define dioctahedral chlorite species. Cookeite is the Li-rich chlorite, whereas sudoite is essentially Li-free. Cookeite and sudoite occur in pegmatite, hydrothermal deposits, and ore deposits. Both have a dioctahedral 2:1 layer and a trioctahedral interlayer (di, trioctahedral chlorite). Donbassite has two dioctahedral sheets (di,dioctahedral chlorite) and is Al-rich. For trioctahedral chlorite, the common polytype is the one-layer, IIb form, although cookeite, commonly forms in the one-layer Ia form (cf., Ia polytype, IIb polytype).
See also Part 1 of the Glossary.
See further explanation under “group names”.
Part 1 of the Glossary:
A group name for platy phyllosilicates of 2:1 layer with a variable layer charge. The interlayer material consists of a hydroxide octahedral sheet, which results in d(001) value of approximately ~ 14.0-14.4 Å. The group is further divided into subgroups that are either trioctahedral or dioctahedral, and these subgroups are further divided into mineral species based on chemical composition.
Terminology commonly used to denote the interstratification of chlorite or chlorite-like layers with smectite or smectite-like layers. Alternatively, this interstratification can be described as chlorite/corrensite. It may be abbreviated as C/S or C-S. Because the interstratification is not regular, it is not recognized as a unique phase.
Cf., chlorite, corrensite, smectite