The results of mathematical modelling of ore breakage by a ball mill based on mathematical models of loaded and unloaded elastic elements are presented. The property of the arrangement of balls in the drum due to segregation is used, under the influence of which they are distributed with increasing size from the loading to the unloading throat, and in the cross-sections from the lining to the axis. It is shown that it is advisable to use the balls in the cross-section of the drum, where their size is 50 mm. The more the volume of ore is destroyed, the more the ball's energy is spent on this, the less energy will be converted into deformation of the elastic element. Consequently, the value of the deformation of the elastic element corresponds to the volume of the destroyed ore, as well as the energy efficiency of its grinding. The approach of interaction of balls with an elastic element from the point of view of mass phenomena will be more effective. The average value of deformations by all balls that have passed through the elastic element, arbitrarily accurately characterizes the average value of the destroyed volume of ore, that is, the energy efficiency of its grinding. The controlled parameter is found in accordance with the proposed relationship with the measured average deformation value of the elastic element. The deviation of certain values from the reference values is within 1%, which meets the requirements of the technological process.