1937 R. E. Grim et al. in Amer. Mineralogist 22 816 There remains only the alternative of giving a new name to the mica occurring in argillaceous sediments, and the term illite, taken from the State of Illinois, is here proposed. It is not proposed as a specific mineral name, but as a general term for the clay mineral constituent of argillaceous sediments belonging to the mica group.

1944 Mineral. Mag. 27 60 Illite is not a stable mineral under humid temperate conditions.

1944 Mineral. Mag. 27 61 According to Fleischer, bravaisite may be the specific mineral species in illites.

1953 R. E. Grim Clay Mineral. iii. 36 Grim, Bray, and Bradley gave the general formula for illites as (OH)₄K_y(Si_{8 − y}·Al_y) (Al₄·Fe₄·Mg₄·Mg₆)O₂₀. In muscovite y is equal to 2, whereas in illite y is less than 2 and frequently equal to 1 to 1·5. According to the formula, illites would include both trioctahedral and dioctahedral types, and no attempt was made to differentiate between biotite and muscovite types of crystallization. At the present time the name illite is generally used, and will be used herein, for clay-mineral micas of both dioctahedral and trioctahedral types and of muscovite and biotite crystallizations.

1957 R. C. Mackenzie Differential Thermal Investigation of Clays x. 260 Studies by Jackson et al. (1952) and Barshad (1954) suggest that illite itself should be considered as an interstratified mineral with mica and montmorillonite layers.

1959 C. S. Hurlbut Dana's Man. Mineral. (ed. 17) v. 463 Illite is the chief constituent in many shales.

1962 W. A. Deer et al. Rock-forming Minerals III. 213 The structure of illite is essentially that of a mica in that it contains layers with a plane of octahedrally coordinated cations sandwiched between two inward pointing sheets of linked (Si, Al)O₄ tetrahedra.

1962 W. A. Deer et al. Rock-forming Minerals III. 214 A less common illite in which sodium is the inter-layer cation is called brammallite (Bannister, 1943).

1972 Nature 28 Jan. 220/1 The essential point about the quickclays is that they contain non-swelling clay minerals such as illite, chlorite and vermiculite, but not montmorillonite.

1949 R. E. Kirk & D. F. Othmer Encycl. Chem. Technol. IV. 31 The illite group of minerals occurs abundantly in marine shales and in many soils, particularly in soils derived from illitic shales.

1963 D. W. Humphries & E. E. Humphries tr. H. Termier & G. Termier Erosion & Sedimentation vi. 153 On the recent volcanic rocks of the northwest coast of Sumatra, H. Erhart (1954) has observed illitic soils between sea level and a height of 4,000 feet.

1972 Nature 28 Jan. 220/1 There are also, however, quickclays containing more than 80% particles finer than 2 μm, mainly of illitic nature.

1657 R. Tomlinson tr. J. de Renou Medicinal Materials i, in Medicinal Dispensatory sig. Qq2^v Deleates black skars, if illited with Oxe-gall.

1657 Physical Dict. Illited, anointed.