Raman microspectroscopy and fluorescence of emeralds from various deposits

Emeralds from nine gem-mining regions in Afghanistan, Brazil, Colombia, Nigeria, Russia, Tanzania and Zambia and a Biron synthetic emerald were studied by non-destructive Raman microspectroscopy and laser-excited luminescence. The experimental results show that the main differences in the Raman spectra of natural emeralds have Raman shifts in the range 100–1700 cm−1. Comparative luminescence spectra of all samples studied are very similar, featuring mainly the Cr ion emission. However, the spectra of emeralds from ‘schist-type’ deposits show moderate shifts of the chromium bands towards longer wavelengths. The samples from Afghanistan are distinct, exhibiting a significantly weaker photoemission. The combination of Raman and luminescence studies is shown to be very useful for the identification of emeralds from various deposits. The results are discussed in terms of the future possibility of creating a spectral data bank for emeralds and other gemstones of different origin.