Dictionary - Definition of ILLITE

Specialty Definition: ILLITE

Domain	Definition
Aerospace	A hydrous mica. See also hydrous mica. (references)
Geological	A potassium-rich clay mineral. (references)
Mining	1: A general term for a group of three-layer (14Aa), mica-like 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. (references)
	2: (i) As a general term, refers to either a discrete non-expansible mica of detrital or authigenic origin or to the micaceous component of interstratified systems, as in illite-smectite. If used to refer to the species, it should meet the following requirements: a) The micaceous layers ideally are non-expansible; b) the octahedral sheet is dioctahedral and aluminous; c) the interlayer cation is primarily potassium; and d) the composition deviates from that of muscovite in two main ways: 1) A phengitic component is present in which substitution of R cations for octahedral Al is balanced by addition of tetrahedral Si beyond the ideal Si:Al ratio of 3:1 for muscovite. This substitution gives the octahedral sheet an overall negative charge of about 0.2 to 0.3 per formula unit; and 2) Interlayer vacancies or water molecules amounting to about 0.2 to 0.4 atoms per formula unit are compensated by additional tetrahedral Si cations beyond those required by the phengitic component. Where reference is made to the species illite, a clear statement should be made to that effect in order to avoid confusion with the general usage. (ii) In soil taxonomy, the presence of a 1 nm x-ray diffraction peak and greater than or equal to 4% KO is used to denote the presence of illite. (references)
Wikipedic	Illite is a non-expanding, clay-sized, micaceous mineral. Illite is a phyllosilicate or layered silicate. Structurally illite is quite similar to muscovite or sericite with slightly more silicon, magnesium, iron, and water and slightly less tetrahedral aluminium and interlayer potassium. The chemical formula is given as (K,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)][http://webmineral.com/data/Illite.shtml], but there is considerable ion substitution. It occurs as aggregates of small monoclinic grey to white crystals. Due to the small size, positive identification usually requires x-ray diffraction analysis. Illite occurs as an alteration product of muscovite and feldspar in weathering and hydrothermal environments. It is common is sediments, soils, and argillaceous sedimentary rocks as well as in some low grade metamorphic rocks. Glauconite in sediments can be differentiated by x-ray analysis. (references)
Source: compiled by the editor from various references; see credits.		Top

Specialty Expressions: ILLITE

Expressions	Domain	Definition
Degraded illite	Mining	Illite that has lost much of its potassium as the result of prolonged leaching. (references)
Sodium illite	Mining	A sodium-rich illite. See: brammallite. (references)
Source: compiled by the editor from various references; see credits.			Top

Extended Definition: Illite

Illite

Structure of Illite mica - USGS.

Illite is a non-expanding, clay-sized, micaceous mineral. Illite is a phyllosilicate or layered alumino-silicate. Its structure is constituted by the repetition of Tetrahedron – Octahedron – Tetrahedron (TOT) layer. The interlayer space is mainly occupied by poorly hydrated potassium cations responsible for the absence of swelling. Structurally illite is quite similar to muscovite or sericite with slightly more silicon, magnesium, iron, and water and slightly less tetrahedral aluminium and interlayer potassium. The chemical formula is given as (K,H₃O)(Al,Mg,Fe)₂(Si,Al)₄O₁₀[(OH)₂,(H₂O)]^[1], but there is considerable ion substitution. It occurs as aggregates of small monoclinic grey to white crystals. Due to the small size, positive identification usually requires x-ray diffraction analysis. Illite occurs as an alteration product of muscovite and feldspar in weathering and hydrothermal environments. It is common is sediments, soils, and argillaceous sedimentary rocks as well as in some low grade metamorphic rocks. Glauconite in sediments can be differentiated by x-ray analysis.

The cation exchange capacity (CEC) of illite is smaller than that of smectite but higher than that of kaolinite, typically around 20 – 30 meq/100 g.

Illite was first described for occurrences in the Maquoketa shale in Calhoun County, Illinois, USA, in 1937. The name was derived from its type location in Illinois. Illite is also called hydromica or hydromuscovite. Brammallite is a sodium rich analogue.

Illite is also used in food supplements, with claimed benefits that range from bowel function to reduction of heavy metals in the blood. Apparently, a French company, Argiletz, provides a wide range of products which are offered for sale in the UK and elsewhere. "Green clay", a term used in several languages, often contains illite. In Scotland, internal uses of illite probably date back to Celtic times.

References

Mitchell J.K. (1993) Fundamentals of soil behavior. Second edition. John Wiley and Sons, Inc., New York. 437 pp, see Chapter 3, Soil Mineralogy, p. 32.

Illite Mineral Data

External links

Source: adapted by the editor from Wikipedia, the free encyclopedia; from the article "Illite". Image Credit.

Topics by Level of Interest: ILLITE
Topics sorted by level of Interest	Level (1=low, 600=high)	Topics sorted Alphabetically	Level (1=low, 600=high)
Illite	6	Illite	6
Source: the editor, created by/for EVE to gauge likely levels of human interest in linguistically triggered topics (compiled across various sources, such as Wikipedia and specialty expression glosses).