THE ROLE OF BERYLLIUM IN BERYLLOSILICATE MINERAL STRUCTURES AND ZEOLITE FORMATION

Abstract

Topological diagrams are constructed for all layered and framework beryllosilicates and for zeolites having related topological features. These diagrams are used to identify the secondary building units (SBU). The SBU are arranged in increasing order of ring dimension to establish a structural hierarchy for this chemical class. Vertex symbols (VS) and coordination sequences (CS) are determined for each unique tetrahedrally coordinated site in every crystal structure. The number sets, VS and CS, identify structural similarities in beryllosilicates and in natural and synthetic zeolites. The frequency of ring-size occurrence varies with Be content in both layered and framework beryllosilicates. Framework density (FD) is derived from structure diagrams, and topological density (TD) is derived from CS sums. Framework density and topological density are strongly correlated. The topological density is controlled by the Be content in tetrahedrally coordinated sites. This structural control could be used to design specific framework arrangements.