Stone is one of the natural materials that are being used from the earliest beginnings of humanity. Today it is used as a building material, and in many cases stone has a decorative and protective role. As it is with other materials, a combination of mechanical, physical and chemical properties condition the ability of stone to process and use. It is impossible, because of its heterogeneous structure, to determine the correct parameters which make the process of treatment stone most effective. For example, the drill when drilling encounters several stone structures that differ in properties, especially hardness and drillability. Drillability indicates easy or difficult penetration of the drill into the material and a good estimation of drillability results in a good estimation of the materials hardness. When processing materials, the cutting part of the tool is being spent. Given that, the drill during operation is subjected to mechanical, thermal and chemical loads that may change the geometry of the blades. A higher degree of process automation and provided tool life has its advantages, suchas reducing the time required for tool change and to avoid possible machine damage caused by the tool wear. That is also positive from the economic point of wiew. By monitoring the degree of tool wear, it is possible to schedule a process with optimal power consumption, maximum tool life and highest productivity and efficiency. This paper describes the influence of rock hardness on the efficiency of the drilling process and tool wear. The aim of the experiment was to analyze signals of cutting forces and motor drive current and evaluate the impact of hardness on the process effectiveness. Samples of stone with different values of hardness were subjected to wear and measurement cycles. In the end, the measured values of hardness were taken into account to evaluate their interaction.