Combination of FTIR and SEM for Identifying Freshwater-Cultured Pearls from Different Quality

Abstract

The freshwater-cultured pearl (Chamberlainia hainesiana species) is an organic gemstone mainly composed of calcium carbonate mineral including calcite, aragonite and vaterite phases. Generally, the quality of freshwater-cultured pearl is based on its luster. The high luster pearl is full of the aragonite phase without vaterite phase. On the other hand, the low luster pearl consists of aragonite and vaterite phases. These data could be proved by the Fourier Transform Infrared (FTIR) spectroscopy combined with the scanning electron microscopy (SEM). As the results, the high luster pearl similarly shows the FTIR spectrum of aragonite phase, and also, it shows the hexagonal shape of aragonite for the SEM image. On the other hand, the FTIR spectrum of low luster pearl has been pointed to the mixture component among aragonite and vaterite phases, and based on the SEM image; the irregular form is also interpreted to the mixture of aragonite and vaterite phases. This research concludes that the quality of freshwater-cultured pearls can be identified by the combination data of FTIR spectra and SEM images. These techniques are suitable for applied gemology.