REFLECTANCE, LUMINESCENCE AND VIBRATIONAL SPECTROSCOPIES FOR THE CHARACTERIZATION OF GEMMOLOGICAL MATERIALS USED IN WORKS OF ART AND HANDICRAFTS

The dependence of several properties of natural gemstones - and of their synthetic analogues and simulants - on the wavelengths of absorbed, emitted or scattered light will be reported and discussed. This approach is non-destructive and does not require any treatment of the sample. FTIR and Raman vibrational spectroscopies are of great help, in particular in provenance studies. Moreover, the micro-Raman technique is invaluable in determining the nature of inclusions. Photoluminescence spectra are mainly determined by the presence of chemical impurities or defects in the crystal lattice. Such features - whether occurring in nature or intentionally introduced - provide useful information about the natural or synthetic origin of an unknown gemstone and possible treatments that it has undergone. A comprehensive research project, concerning a low-cost portable apparatus for application of the above-outlined methods to gemmological problems is at present in progress.