The effect of compression on the magnetization of rocks has been examined for the dependence of the structure on the magnetic fraction and on its composition. The change in magnetization under compression depends on such parameters as coercive force, saturation remanent magnetization, magnetic susceptibility and coercivity. The measurements were carried out for three groups of samples containing three sets of magnetic minerals. The stress dependence of magnetization varies for each group. The dependence of susceptibility and irreversible magnetization on compression was examined. It is revealed that these relations are also different for each group of samples, and depend on the composition of the magnetic fraction and the state of internal stresses.