A series of melting experiments was carried cut at 1 650°C and 1.00–3.00 GPa using alkaline basalt as starting material. The cornpitions of quenched basaltic glasses in the products were detected by electron micro probe. Their CIPW norms were calculated and their refractive indices were determined by the oil-infused method. The Raman spectrum of the quenched basaltic glasses indicates that their main structural species are monomer [Si2O4]14 , chain [Si2O6]14- and sheet [Si2O5]12-. The relationship at the same temperature between the proportions of integrated areas of structural species, and compositions and pressures was discussed.