The resistance of rocks to brittle failure depends on both the elasticity of the minerals present and the internal microstructure, both parameters then affect the failure of rocks under loading in simple pressure or tension. Fragile failure involves the formation of new microcracks, their association and final decay, and critical levels of failure can be reliably derived from the working diagram. In contrast to the empirical and often ad hoc chosen test procedures for determining the mechanical resistance of rocks for crushed stone, the proposed project will focus on solving the problem using laboratory tests of mechanical properties and detailed analysis of rock composition (mostly volcanic) and their microstructure. Deformation and energy parameters calculated from the working diagram will be correlated with brittleness and stiffness, and with the results of mechanical stability tests, including resistance to crushing. The combination of data on composition and internal structure and experimentally determined deformation behavior will be used for advanced analysis of technological-mechanical stability tests as a tool for more reliable prediction of crushed stone life.