For a series «beryllian indialite - Õ» (Õ = BeO, MgO, Al2O3, SiO2) is experimentally proved, that the substance of the beryl structural type at lower solidus temperature are derived in changing to Õ up to (rel.%) ~220 % MgO, ~420 % Al2O3, ~22 % SiO2 and further than 500 % ÂåÎ. The single beryllian indialite-based solid solutions are derived in up to ~30 rel.% Al2O3 and ~200 rel.% BeO and, probably, are not formed in series «beryllian indialite - Õ» (Õ = MgO, SiO2).