The mounted semi autogenous (SAG) mill in the processing unit of the Midouk copper mine which consumes 35% of operational costs has a critical size within the range of 2.5-5 cm. To optimize the energy consumption in the milling unit of the mine, the data have been collected from 36 blast blocks. These blocks are selected in the main ore body area to monitor their effects on energy consumption in the milling unit. Owing to the dependence of mill energy consumption on the feed strength properties, a criterion for mill performance (MPC) has been defined and compared with the obtained dynamic hardness of seven specific blasting blocks. The results show a linear relationship with the accuracy of R 2 = 0.91 between the dynamic hardness and the MPC. For mines that use SAG or AG mills, the energy consumption for crushing the unit weight of feed depends on their dynamic stiffness.