A method for characterizing nature of a material, including: providing at least one sample of the material between an X-ray source and a detector; using the X-ray source to make N X-radiation spectra transmitted through the material, each for a time; calculating transmission function of the material as a function of energy or the detection channel; and in each of at least two energy zones, calculating the integral of the transmission function, thus forming at least a first transmission coefficient and a second transmission coefficient.