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(Minerals) a clay mineral of the mica group, found in shales and mudstones. Crystal structure: monoclinic. Formula: K1–1.5Al4(Si6.5–7Al1–1.5O20)(OH)4
[C20: named after Illinois, where it was first found]
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014


(ˈɪl aɪt)

any of a group of clay minerals, hydrous potassium aluminosilicates, characterized by a three-layer micalike structure and a gray, light green, or yellowish brown color.
[1937; Ill(inois) + -ite1]
il•lit•ic (ɪˈlɪt ɪk) adj.
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References in periodicals archive ?
For example, the smectite peak, vermiculite illite peak, and kaolinite-smectite peak all could be detected after XRD-profile fitting.
Analysis of some properties of model system from lowmelting illite clay and fibrous mineral wool waste, Material Science-Poland 25(1): 209-217.
Analysis results showed kaolinite, illite, montmorillonite and quartz, an iron oxide content of 1.8 per cent, titanium low at 0.13 per cent, alkalis at 5 per cent and calcium oxide also low at 0.03 per cent.
The IR was mainly represented by a muddy fraction (<0.01 mm) consisting pre-dominantly of illite accompanied by a considerable amount of chlorite.
The adverse effect of illite clay on bitumen recovery was found to be related to its acidity.
Diffraction intensity ratios (Dis) of the clay fraction (<2.0 [micro]) were calculated by measuring the area under the illite peak at 1.0 nm and dividing it by the area under the kaolinite and chlorite peak at 0.7 nm (Willman and others 1966; Bruno and others 2006).
There are several different types of silicate clay minerals: illite, vermiculite, smectite, and kaolinite.
X-Ray diffraction analysis of clay samples showed a mixed assemblage of kaolinite, smectite, and illite clays, as well as a large quantity of quartz.
As a rule it has altered to albite, illite or carbonates.
The layers of one mica clay, illite, are firmly bound by bridges of potassium ions.
Small quantities of illite (and probably sapo-nite), opal, "wad", and calcite were also encountered.