An initial value induction problem has been solved to examine the response of a massive sulphide ore body under conditions of common occurence. The generalized expression for the induced field due to a step-function dipolar field in the presence of a non-uniformly conducting permeable sphere surrounded by a finitely resistive overburden has been derived. Two cases, when the concentric shell is (i) insulated from and (ii) in galvanic contact with the inner core, have been considered. The analytical results are in computable form to yield the decay-characteristics for application in geoelectromagnetics. Particular cases of the problem treated by the other investigators are discussed.