In order to improve the performance of mine workings development technologies is necessary to establish optimum process parameters for drilling - blasting operations, as a function of the geo-mechanical characteristics of rocks. The most important condition for successful drilling - blasting operations, with respect to the technical, economic and safety point of view, is a realistic projection of their choice, both in terms of explosive materials and concerning the operating parameters. The most important characteristics of rocks which give guidance on the excavation by drilling - blasting are: compressive strength and abrasiveness of rocks. The paper deals with the speed of drilling and explosive specific consumption for the two strength characteristics of rocks.