An analytical and transmission electron microscope study showed that nonequilibrium gas-to-solid condensation in an AlO-SiO vapor yielded solid units with well defined compositional peaks at 11.5 wt % Al2O3 and 41-47 wt % Al2O3. These peaks coincide with metastable eutectic points in the Al2O3-SiO2 phase diagram. The compositions of thermally annealed units support the presence of a (metastable) miscibility gap between similar to 15-similar to 60 wt % Al2O3. The important finding in this analysis is the determinative role of metastable eutectics in nonequilibrium gas-to-solid condensation.