The elastic and indentation behaviours of silicate glasses with different compositions were investigated and interpreted in the light of structural analysis, using MAS-NMR and neutron diffusion experiments. The coordination numbers, as well as the interatomic distances and the number of bridging oxygens per tetrahedron were experimentally determined. Largest elastic moduli and hardness values are obtained for the grades which have the lowest silica contents, or in other terms for glasses with a high glass network filling rate in comparison to the open and flexible network of vitreous silica. The silicon content also plays a major role in the indentation behaviour by favouring flow densification beneath the indenter. The lower the Poisson's ratio, or the bulk modulus or the glass compactness, the more anomalous is the glass behaviour.
