Glassy materials for HLW immobilization were produced from HLW surrogate, quartz sand, datolite (CaBSiO4OH), and bentonite clay at a temperature of up to 1200 °C. Waste loading (WL) ranged between 20 and 40 wt.%. The glasses were characterized by X-ray diffraction, scanning electron microscopy and Fourier-Transform infrared spectroscopy. Glasses with waste loading of up to 35 wt.% obtained by melt pouring onto a metal plate were found to be rather homogeneous but contained minor noble metal oxides and britholite (at high waste loadings) while those annealed in turned-off furnace were partly devitrified. Average chemical composition of britholite corresponded to formula Na1.00Ca4.02Y0.33Ce0.05Nd3.64Gd0.17Si6.79O24.39. The glass network is built from SiO4 units with one or two bridging oxygens and complex borate groups with primarily ternary coordinated boron. Increase of waste loading resulted in shift of band’s maxima to lower wavenumbers exhibiting increasing the fraction of SiO4 unit with lower number of bridging oxygen ions and thus reduction of glass network connectedness. Glasses with up to 30 wt.% waste loading kept their high hydrolytic durability making them suitable for HLW immobilization.