The behaviour of samples studied in an electric field at microwave frequency is characterised by the real and imaginary part of complex dielectric permittivity. Knowledge of these parameters permits us to predict the running of microwave heating. The article describes the influence of temperature on the change of real and imaginary permittivity of andesite, sulphide and carbonate samples at the frequency of 2216 MHz. The permittivity was measured by the resonant cavity method. The heat and Maxwell's equations were simultaneously solved using the COMSOL MULTIPHYSICS programme to predict and visualize the temperature rise in the samples exposed to microwave radiation. (C) 2010 Elsevier Ltd. All rights reserved.