An attempt is made here to model the complex resistivity effect which is utilized in the geophysical exploration for disseminated sulphide mineralization. A model of a hypothetical mineral grain is developed, and the complex resistivity of a medium loaded with such grains is studied. First, quasistatic electrical conditions (Wait, 1982) are used so that the problem can be solved by using potential fields. The equations are developed in spheroidal coordinates; however, a uniform nonconfocal grain surface impedance is used that does not allow a closed-form solution (Wait, 1958, 1983α). Therefore, approximate solutions are obtained by using numerical techniques (Flanagan, 1983). Sample calculations of complex, frequency-dependent resistivities of a hypothetical pyrite ore are presented. These calculations are based on experimentally determined surface impedance data for pyrite, taken from the literature (Olhoeft, 1982; Collett, 1959).