Mechanism of the Formation of Regular Structures of Noble Opal Films on the Surface of Solid Bodies

摘要

In the opal-bearing provinces of Australia, one can observe a porous system of large sandstone bodies filled with noble opal or a thin coating of noble opal on quartz and feldspar grains. The thickness of such films may be equal to only a few layers of monodisperse spherical silica particles (MSSP), and they can be detected in the course of microscopic examination only due to diffraction effects. It is rather difficult to imagine their formation as a result of sedimentation or of the fil-trational concentration of MSSP suspensions together with the subsequent permolecular crystallization . It is more reasonable to regard the mechanism of pore filling in sandstones as a consequence of the capillary suction of MSSP suspensions, resulting in the formation of regular film structures that consist of MSSPs on the basis of surface phenomena with the participation of the phase boundary. Since the driving forces of regular structure formation in films are quite distinct in this case, the question arises as to whether this process represents an instance of permolecular crystallization or a forced MSSP stacking in the regular structure. This question has not been considered as yet; nor has the mechanism providing the formation of noble opal film been studied in detail.