Hard soils and weak rocks present special features that make them basically different from either soils or rocks. In fact, the well known influence of the void ratio on hydraulic and mechanical properties of the soil is obscured by that of interparticle bonds and of fissures. On the other hand, since bonds can easily fail as a consequence of mechanical and/or environmental processes (weak bonds), time dependent changes in hydraulic and mechanical properties represent a peculiar issue that should be properly taken into account in all practical problems. The paper focuses on these points, often disregarded by researchers and professionals, suggesting that only a full development of a specific branch of Geosciences dedicated to hard soils and weak rocks would lead to advanced and structured approaches for the analysis of engineering problems.