The refractive index and the relative changes in the density for LiAlSi3O8 glass in the pressure range up to 6.0 GPa were obtained using a polarization-interference microscope and an apparatus with diamond anvils. The results were compared with the previous data for the NaAlSi3O8 and KAlSi3O8 glasses. The compressibility of glasses increases in a series of alkali metal cations Li+, Na+, K+. From the previously found dependence of the compressibility (at P=4.0 GPa) on the degree of depolymerization the value of NBO/T = 0.31 for LiAlSi3O8 glass was calculated. A high degree of depolymerization of the LiAlSi3O8 glass indicates not only a high content of NBOs atoms in the structural network, but also the presence of highly coordinated aluminum (according to the literature data similar to 9%). The proposed schematic reaction for the formation of different structural groups corresponds to the condition of the existence of 9% highly coordinated aluminum. (C) 2015 Elsevier Ltd. All rights reserved.