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- Clay
mineral family of hydrous aluminous silicates.
Structure is similar to that of
montmorillonite, but aluminum replaces 10 to 15
percent of silicon, which destroys montmorillonite's property of expanding with addition
of water because weak bonds replaced by strong potassium-ion
links. Structurally illite intermediate between montmorillonite and
muscovite. Montmorillonite converts to illite in
sediments; illite, to muscovite under conditions of low-grade
metamorphism. Illite is commonest clay mineral
in clayey rocks and recent marine sediments and is
present in many soils.
Source: Leet, L. Don. 1982.
Physical Geology, 6th Edition. Englewood Cliffs, NJ: Prentice-Hall
- A general term for a group of three-layer (14Aa), micalike clays (K,H (sub
3) O)(Al,Mg,Fe)2 (Si,Al)4 O10 [(OH)2 ,H (sub
2) O] ; widely distributed in argillaceous sediments and derived soils;
intermediate in composition and structure between muscovite and
montmorillonite; contains less potassium and more water than muscovite,
but more potassium than kaolinite or montmorillonite; potassium is
generally replaced by calcium and/or magnesium; named from studies by
Grimm of shales and clays in Illinois. See also: muscovite CF: pholidoide; phyllite. Syn: hydromica; hydromuscovite; glimmerton.
Source:
Dictionary of Mining, Mineral, and Related Terms
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