An industrial term for clay minerals (especially palygorskite, sepiolite, Na- or Na- exchanged montmorillonite, hectorite, and organoclay) having a high slurry viscosity at low percent solids when mixed with fluid. Such clay minerals form a colloid where the dispersed phase and the dispersion medium produce a semisolid material, similar to jelly. Industrial applications include thickening/suspension agents, adhesives, sealants, putties and glazing compounds. Jelling viscosity is typically measured on Fann or Brookfield viscometers. For aqueous applications and some fibrous clay minerals such as palygorskite, the gelling behavior and viscosity is enhanced by adding magnesium oxide or by extruding the slurry to align the needle-shaped crystallites. For montmorillonite, gelling behavior can be enhanced by soda ash treatments to increase the exchangeable Na-cation content and the swelling capacity of the clay mineral. For solvent-based applications, various smectites can be surface modified by quaternary-amine compounds to form organoclays that display superb gelling characteristics.
See colloid

A discredited term, a mixture of pimelite and Ni-rich serpentine.

The deliberate ingestion of (specifically) soil/clay; a form of pica.
Cf., pica

Geopolymers are inorganic binders used as cement substitutes. Geopolymers are made from activated (commonly heated or milled) silicate or aluminosilicate materials and are composed of poorly crystalline Al, Si networks. Commonly, thermally activated clay, i.e., metaclay (often metakaolin) is used, but geopolymers can be produced from feldspar, impure clay-rich interstratifications, waste product from coal combustion or metallic ores, fly ash or other ash material, iron oxides, or ground blast-furnace slag. These starting materials are mixed with an alkali or alkaline earth metal hydroxide solution such as KOH, NaOH or Ca(HO)_2M (= alkali activation). The alkali or alkaline earth metal hydroxide solution dissolves Al, Si and alkali or alkaline earth elements. During the hardening process, the dissolved species polymerize to form a network characterized by short-range ordering. The name geopolymer is derived from “geo”, which refers to the origin of the precursor, and “polymer”, which refers to the linking of molecules in a repeated fashion.
Cf., alkali activation, blast-furnace slag, geopolymerization, glass, metaclay, metakaolin, thermal activation

The process of forming geopolymer cements. The gel-like mixture of the activated starting material (often metaclay) and the alkaline solution hardens upon drying by evaporation of water, forming a three dimensional inorganic network (geopolymer) by polymerization of Al and Si.
Cf., geopolymer, hardening, metaclay

Commercialized therapies using geologic materials, such as peloids, or processes, e.g., hot springs or mud baths.
Cf., peloid, pelotherapy

A thermodynamic state property useful to determine the spontaneity of a reaction within a system (without regard to the surroundings as is the case with entropy changes) and the direction of the reaction. The change in Gibbs energy, ΔG, is equal to ΔH – TΔS, where ΔH is the change in enthalpy (cal/mole), T is the absolute temperature (K), and ΔS is the change in entropy (cal deg^-1 mole^-1). A substance reacts if the change in Gibbs energy is negative going from the initial state to the final state. Gibbs energy is often referred to as Gibbs free energy.
See enthalpy, entropy, state function

A polymorph of Al(OH)₃ where one third of the octahedral sites are vacant and each OH group is coordinated by two Al cations. Although each layer is approximately closest packed, the stacking of layers is not closest packed, and OH groups in adjacent layers superpose. The interlayer OH to OH distance is relatively small (at ~2.78 Å), indicating a strong hydrogen bond that is enhanced by strong polarization caused by the highly charged Al³⁺ cation.
Cf., bayerite, nordstrandite

A term that is synonymous with the dioctahedral interlayer sheet in chlorite. This sheet is analogous to gibbsite in that gibbsite consists of two (intralayer) planes of closest packed oxygen atoms with two out of three of the octahedral sites between the two planes occupied by trivalent cations, in this case Al. In the gibbsite-like sheet, some of the oxygen atoms are replaced by hydroxyl groups, (OH). This term is only for chlorite. The dioctahedral sheet in a 2:1 layer silicate, such as mica, is very different from gibbsite, whereas the interlayer in a chlorite is quite “gibbsite-like”. For example, in a 2:1 layer octahedral sheet, two thirds of the oxygen anions are apical oxygen atoms whereas only one third are OH groups—very different from a gibbsite-like sheet.

A poorly defined material, possibly muscovite and cordierite.