The change of a material structure can reasonably affect its electrical properties. Changing the thermodynamic equilibrium by applying stress on a geomaterial sample, current emission can be stimulated. This kind of emission can be detected experimentally. In the experiments described below various modes of stress change were applied. Stress was increasing with various stress rates, constants or not, until the fracture of the samples. During the experiments current emissions were studied. Results show that the stress rate influences the PSC values but the total charge released by this process does not seem to vary considerably for the various stress rates.