BeO·Al2O3·SiO2 system: Structural relationships of crystalline, glassy, and molten beryl

Physical property measurements are reported for beryl glass and for three 60 mole % SiO₂ melts (including beryl) at temperatures above 1600° C. Electron micrographic evidence shows that beryl glass has undergone a two-liquid phase separation. Density measurements of this glass and its melt can be interpreted in terms of the dissociation of Si₆O₁₈^-12 rings as beryl melts incongruently. The presence of discrete BeO₄ tetrahedra and AlO₆ octahedra in molten beryl is suggested by the electrical conductance and viscosity data for these melts.