The aim of this work is to show whether or not a relationship exists between the different volumetric strain quantities and to assess also whether the volumetric quantities are related to the different types of volumetric strain curves under failure-deformation process of hard brittle rocks. Tests were conducted to determine the complete stress-strain curves of different 83 rocks types under uniaxial compression using a closed loop servocontrolled testing system. The rocks failure-deformation behaviours curves were characterized and coordinated into groups of three different types of volumetric strain curves. The volumetric strain quantities were estimated which include, the elastic volumetric strain, slope of the normalised stressvolumetric strain curves and the maximum total volumetric strain. These volumetric strain quantities were compared with each other. The result show that the volumetric strains quantities are related by power form law. The volumetric strain quantities were also compared for each group of the three types of volumetric curves. It was established that there is connection between the volumetric strains quantities and the types of the volumetric strains curves. The relationship show a power form law and the curves become more concave from type one to type two and type three volumetric strain curves respectively.