A process of separating, fractionating, or manipulating fine particulate materials (or lighter particles) by gravitation in a vertically directed, usually upwards, moving air stream. This method is typically used for particles with sizes greater than 1ìm. The smaller or lighter particles rise to the top (overflow) above the coarser heavier fractions (underflow) because their terminal velocities are lower than the initial velocity of the rising fluid. The terminal velocities of various particle sizes in any media is calculated by Stokes’ law.
See also Stokes’ law;
Syn., elutriation

A process where kaolin is dried, transported on a column of rapidly moving air through a pulverization mill, and passed through a cyclonic air-classifier where coarse, sand-size particles are removed as gangue or returned to the mill for further size reduction. The term is used in the kaolin industry and refers to the less costly, dry-processed and air-classified powder products where bulk chemistry is of concern, but where purity, handling, and appearance may be less important.
Cf., air classification

See feldspar, alkali feldspars.

A regularly ordered interstratification of a talc-like layer and trioctahedral smectite-like layer in a ratio of 1:1 (Veniale and van der Marel, 1969; Bailey, 1981).
Cf., interstratification

An alkali activated clay involves the addition of alkali or alkaline earth metal hydroxide solutions such as NaOH, KOH or Ca(OH)2 to partly or completely dissolve clay mineral particles. Clay minerals are commonly calcined prior to alkali activation to increase the amount of dissolved species. After hardening, the product is a geopolymer, and the process is referred to as alkaline activation, although both alkali and alkaline earth elements may be involved.
Cf., activated clay, alkaline activated clay, geopolymer, thermally activated clay

Alkali feldspars represent a subgroup of feldspar minerals occurring in the solid solution series between albite [Ab: Na(Si3Al)O8] and orthoclase [Or: K(Si3Al)O8] end members. The series includes minerals of albite, sanidine (a high-temperature monoclinic polymorph of K-rich feldspar with disordered Al-Si distributions, occurs in lava flows), microcline (triclinic polymorph of K-rich feldspar, may be referred to as low, intermediate and high for variations in temperature of occurrence, and “maximum” with ordered Al-Si distributions), adularia (a K-rich feldspar with monoclinic and triclinic domains formed from partial Al-Si order states, often designated as a varietal name, occurs hydrothermally, in pegmatites and under diagenetic conditions), and orthoclase (a K-rich feldspar with an intermediate Al-Si ordering state, occurs in small plutons at moderate depths). The boundary between albite and sanidine is at ~ Or40 (i.e., ~ 40 mole % of K-rich feldspar) and this region between Ab90 to ~Or40 (with <10 mole % of anorthite component) is also defined as “anorthoclase”. Cf., feldspar

An alkaline activated clay is a clay treated with Na₂CO₃ (soda activation) to increase the proportion of Na-exchanged smectite or the addition of alkaline solutions to increase the pH of the clay aqueous suspension. In either case, bacterial growth is promoted (ageing).
Cf., activated clay, ageing

A method to determine the layer charge of phyllosilicates with 2:1 layers, primarily those phyllosilicates with interlayer-cation exchange capability, interstratified complexes, and micas. The layer charge is determined based on changes in basal spacing [d(001) value] as derived from various alkyl-chain lengths (C6-C18) of alkylammonium cations, following exchange in solutions with a series of n-alkylammonium hydrochloride salts (Lagaly and Weiss, 1969; Lagaly and Weiss, 1975). Alkylammonium-exchanged, low-charge smectites produce smaller basal-spacing values than higher-charge smectites or vermiculites. Greater expansion is produced by n-alkylammonium salts with longer alkyl chain lengths. Layer charge is estimated from the monolayer to bilayer transition alkyl-chain length. See Lagaly (1994) for further description, problems, and history.
Cf., alkylammonium organoclay bilayer, alkylammonium organoclay monolayer, alkylammonium organoclay paraffin complex, alkylammonium organoclay pseudotrilayer, organoclay

An interlamellar arrangement of one layer of alkylammonium cations with the C-C-C plane of the alkyl chains (n < 8) parallel to the (001) plane of the 2:1 layer to produce a characteristic 13.6-Å spacing of a phyllosilicate. The positively-charged end groups (e.g., NH₃⁺) of the alkylammonium cations are attached to alternate siloxane surfaces in the interlayer.
See Lagaly and Weiss (1975); Lagaly (1994).
Cf., alkylammonium layer charge method, organoclay

An interlamellar arrangement of alkylammonium cations with the positively-charged (polar) end groups (e.g., NH₃⁺) of the alkylammonium cations attached to the interlayer silicate surfaces of a 2:1 phyllosilicate. The alkyl chains are tilted from a perpendicular orientation with respect to the (001) surfaces, and this orientation produces basal spacings of>22Å. The angles between the alkyl chain axes and silicate 2:1 layers increase with layer charge and range from 50 to 60° in vermiculites and to 90° in micas.
See Lagaly and Weiss (1969; 1975); Lagaly (1994).
Cf., alkylammonium layer charge method, alkylammonium organoclay bilayer, alkylammonium organoclay monolayer, alkylammonium organoclay pseudotrilayer, organoclay