A metastable lithium-beryllium-aluminum silicate with a β-spodumene structure

Abstract

A metastable lithium-beryllium-aluminum silicate “Li_0.34 Be_0.88 Al_0.66 Si_1.98 O₆” was prepared by the thermal treatments of a lithium-bearing beryls and of a lithium-free beryls loaded by lithium chloride at temperatures from 620°C to 1, 170°C in air. It is tetragonal with a=7.502, c=9.120Å, Z=4, sp. gr. (obs)=2.33±0.11, sp. gr. (calc)=2.33, n=1.533±0.001, very low birefringence and isotypic with β-spodumene. Rate of formation of this phase was notably affected by temperature, duration of the heating, lithium concentration and grain size of original beryls. On prolonged heating, it decomposed into the other phase assemblage, suggesting its metastable nature.