Abstract: Method and apparatus for radiological investigation of subterranean multicomponent media such as borehole fluids, and subterranean earth formations. The formation under investigation or other medium is irradiated with penetrating radiation having a plurality of discrete energy levels. The radiation at the several energy levels may be applied simultaneously or sequentially. In either case, the absorption of the applied radiation within the medium under investigation varies from one energy level to another. Radiation emanating from the medium is detected for each of the discrete energy levels and the intensity of the detected radiation for each energy level is correlated with the intensity of the applied radiation for each of the energy levels.