Infrared absorption micas

Laperche V, Prost R (1991) Assignment of the far-infrared absorption bands of K in micas. Clays Clay... 

Tateyama H, Shimoda S, Sudo T (1977) Estimation of K-0 distance and tetrahedral rotation angle of K-micas from far-infrared absorption spectral data. Am Mineral 62 534-539 Tillmanns E, Zemann J (1965) Messung des Ultrarot-Pleochroismus von Mineralen. I. Der Pleochroismus der OH-Streckfrequenz in Azurit. N Jb Mineral Mh 1965 228-231 Tsuboi M (1950) On the position of the hydrogen atoms in the crystal structiue of muscovite, as revealed by the infra-red absorption study. Bull Chem Soc Japan 23 83-88 Vedder W (1964) Correlations between infrared spectium and chemical composition of mica. Am Mineral 49 736-768... 

There have been several detailed and careful studies in this field recently. For example. Farmer and Russell [1964] have studied the infrared absorption bands arising from the structural hydroxyl groups of a number of layer silicates, i.e., in the region from 3500 to 3700 cm" . They attempted to assign the two frequencies they observed in terms of either octahedral substitutions or of Al-for-Si substitution tetrahedrally. They confirmed earlier work that in the dioctahedral micas such as muscovite, the OH dipole oscillations lie at around 16° to the plane of the sheets, whereas in the trioctahedral micas, the O—4 bond is normal to the plane of the sheets. 

Jorgensen, P., 1966. Infrared absorption of 0—H bonds in some micas and other phyllosilicates. Clays Clay Min. 13 263. 

Lyon, R. J. P., and W. M. Tuddenham, 1960. Determination of tetrahedral aluminum in mica by infrared absorption analysis. Nature 185 374. 

Titeica, R., and G. Palade, 1959. Infrared absorption spectra of some micas. Rev. Phys., Acad. Rep, Populaire Roumaine 4 93. 

The most recent trend in infrared studies, therefore, seems to be toward a careful study of well-characterized specimens, (e.g., micas having nearly end-member chemical composition) and using infrared techniques of polarized radiation and high resolution (about 6 cm" ) spectrographs. By the latter means, the fine structure of the absorption bands can be determined, The aim in so doing is to test theoretically calculations about the interaction of possible lattice vibrations with the fundamental frequency due to, say, the OH-stretching vibration. 

Infrared observations of decreased intensity of OH absorption bands at elevated temperatures have played a major part in Fripiat s arguments for a predehydroxylation state characterized by high proton mobility in layer silicates and hydroxides (Fripiat and Toussaint [1963] Fripiat et al. [1965] Fripiat et al. [1967]). The results obtained with micas are now known to have been affected by radiation from the heated sample the intensity decrease is generally a minor effect, except for the special case of boehmite (Cant and Hall [1968]). 

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