On the Phase Associations and Crystal-Chemical Inheritance of Be–Mg–Al Silicates during Subsolidus Crystallization

During the solid-phase synthesis of Be–Mg–Al silicates, i.e., beryllian indialite (BI), the crystal-chemical proximity is due to the transfer of elements of chemical and structural inheritance. BI crystallization from a gel is carried out via the structural adaptation of multicomponent metastable phases transforming into BI, which is implemented in two stages: diffusion and the formation of microcrystallites fed by a melt film. During the sintering of dry oxides, parageneses are transferred from a previous temperature stage to the subsequent one so that several phases of the former stage are retained and the fraction of stable phases increases because of the consumption of intermediate phases. Phase transformations whereby BI is crystalized in the subsolidus region are interpreted from the viewpoint of the evolutionary regularities of mineralogenesis.