Characterization and discrimination of some gem silicate minerals adopting LIBS, FTIR, and Raman spectroscopic techniques

Abstract

In this paper, characterization and discrimination of some silicate gems (gemstones and low-gem quality varieties) from ancient Egyptian mines have been performed for the first time adopting molecular and elemental spectroscopic techniques. The selected gem groups are peridot, beryl/emerald, amazonite, and amethyst. In this sense, characterization of the genuine Egyptian gems and the importance of mineralogical and chemical signatures in a historical context as well as the scope of geoheritage can be achieved for the first time. Laser induced breakdown spectroscopy (LIBS) analysis has been found to be an effective method for the discrimination among different gems groups where a characterizing element for each group in a specific spectral window has been found. Raman and Fourier transform infrared (FTIR) spectroscopy spectra have proven to be fingerprints with the ability to distinguish future alteration of the gemstone depending on the molecular vibrational spectroscopy. FTIR provides the functional group that can absorb the infrared radiation and be responsible for the coloring of the gemstones.