THE MECHANISM OF SUPRAMOLECULAR CRYSTALLIZATION IN SUSPENSIONS OF MONODISPERSE SILICA SPHERES DURING THE FORMATION OF PRECIOUS OPAL

Abstract

Active participation of dispersed and colloidal systems in hypergene and hydrothermal processes favors supramolecular crystallization during mineral formation. We discuss the mechanism of this crystallization by the example of monodisperse silica suspensions. The phase transition from suspensions to supramolecular crystals occurs at the limiting concentration of structural units ("dense liquid") according to the model of Alder-Hoover. The kinetics of the interface motion is described by the Frenkel theory of liquids and solids. The linear growth of the crystals follows the model of the rough interface and is described by the equation derived from the Frenkel theory. We also discuss the mechanism of crystal growth which takes into account polarization of structural units, dipole-dipole interactions, and nonspherical particles involved in geological processes. In this case layer-by-layer and screw dislocation growth may occur.