Nuclear forensics of a colored gemstone: evidence of proton bombardment of a blue topaz.
A blue topaz was investigated radiologically for forensic purposes. It clearly exhibited detectable activities of (22)Na (0.28 ± 0.01 Bq). The occurrence of this artificial radionuclide evidences fraudulent irradiation of the gemstone with protons to give it its blue color. It can be assumed that also (7)Be must have been produced in the course of proton bombardment, yielding even greater activities than (22)Na. Since no traces of short-lived (7)Be could be detected, the topaz must have been irradiated at least 300 days prior to measurement.