Disclosed herein is a system for non-destructive classification of specimens. The system includes an e-beam source, an X-ray measurement module, and a computational module. The e-beam source is configured to project e-beams on a specimen at one or more e-beam landing energies, so as to penetrate the specimen and induce emission of X-rays. The X-ray measurement module is configured to measure the emitted X-rays. The computational module is configured to process the measurement data to obtain an energy signature of at least one target substance included in the specimen and classify the inspected specimen based on the obtained energy signature and one or more reference energy signatures pertaining to one or more reference specimens, respectively.