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We have been unable to confirm the recent report that kaolinite catalyzes the polymerization of aqueous d- and l-aspartic acid at different rates. In experiments where dl-Asp was used, no induced optical rotation was found in the reaction solution. No evidence for polymer (or other product) formation was found when l-Asp-2-C was used, and products were searched by paper chromatography and X-ray film autoradiography. Asp is adsorbed by kaolinite, but no selectivity for one or the other enantiomer was observed. [ABSTRACT FROM AUTHOR]

The paper presents the dynamics of the structural change of kaolinite and its polymorphous (polytype) modifications at different stages of sedimentary rock formation. Sedimentogenesis is characterized by a gradual disordering of structure of triclinic kaolinite, the degree of disorder produced being proportional to the intensity and duration of the influence of the hydrodynamic medium. Epigenesis (deep) is connected with gradual transformation of kaolinite into dickite through the stage of mixed-layer growths inheriting the structure of twin rotations of disordered kaolinite from the sedimentogenesis stage. In metagenesis filling of fissures with dickite or nacrite takes place. The former is peculiar to the general thermodynamic medium of deep epigenesis/metagenesis, whereas nacrite is an indicator of intense stress and seems to be due to transformation of dickite. [ABSTRACT FROM AUTHOR]

Analyzes a study conducted by the author on clay-mineral diagenesis and presents information on the transformation of sheet silicates. Stages in the diagenetic evolution of clay minerals; Crystallochemical processes that take place during the diagenetic evolution of clay minerals; Description of the formation of kaolinite mineral.

The structure of multiplayer polytype modifications of layer silicates may be regarded as the result of a combination of regularly oriented single layers. Accordingly, the optical constants of a single layer (of a monolayer polytype modification) may be used for the calculation of optical constants of any other multiplayer polytype modification of a given type of layers. The formulas connecting the constants of a polytype modification of layer silicates have enabled the establishment of the main parameters (Ng, Nm, Np, 2V) of the muscovites 1M and 2M[sub2] according to the known optical constants of the muscovite 2M[sub1], and the computation of the new constants of kaolinite and nacrite based on the known parameters of dickite. The optical constants established theoretically were confirmed by direct measurements for muscovite 1M, muscovite 2M[sub2] (gümbelite) and kaolinite. The optically positive character of kaolinite with +2V = 25° has been established. The assumption of the optical mixibility of finely dispersed polyminerallic media, in which the dimensions of monotype crystals are smaller than the visible light waves, made it possible to determine the quantitative relations of clay minerals in the mixtures based on optical constants of oriented aggregates. [ABSTRACT FROM AUTHOR]

In order to obtain data comparable to those of BISCAYE (1965) on the Atlantic Ocean, the authors carried out quantitative X-ray determinations of clay minerals in the sediment.s of the Indian and Pacific oceans using the Biscaye-method. The latitudinal localization of clay minerals in the bottom sediments of the world ocean is determined with. the help of schemes of area localities. Two groups of minerals are distinguished according to their location. The first group consisting of kaolinite, gibbsite and montmorillonite, is concentrated in. maximum quantities in tropical-humid zones (mainly in latitudes 35°N and 35°S), and has an "equatorial"-type distribution. The second group containing chlorite and illite is located in moderate and high latitudes, chiefly with cold, moderately humid and ice zones forming a so-called "bipolar"-type distribution. [ABSTRACT FROM AUTHOR]