Crystal chemistry of silicates with three-layer TOT and HOH modules of layered, chainlike, and mixed types

Abstract

In view of new data on the chemical composition and structure of a series of natural layered silicates containing three-layer blocks and their corresponding microporous minerals with related fragments, their structural features; the structural conditionality of their properties; their transformation in the presence of isomorphism, decationation, and hydration; and the problems related to typomorphism and some other questions urgent for modern mineralogy have been considered. The structures are described in terms of threelayer modules of different forms and dimensions that are present in these structures. The composition and design of the general structural base of related series—three-layer modules forming layered or linear radicals—are also discussed. The minerals of these families differ in chemical composition, symmetry, and unit-cell parameters, as well as in the topological features associated with the type of condensation of the Si tetrahedra into layers or ribbons and the degree of condensation of M polyhedra in the central part of blocks: from layers and octahedral ribbons of different widths to chains and isolated polyhedra.