Multi-excitation photoluminescence spectroscopy system for gemstone analysis

Luminescence spectra can reveal important chemical and structural information that can be used for gemstone characterization and identification. Traditionally, gemstone UV-excited luminescence is evaluated visually under mercury vapor lamp illumination. This approach is limited by several factors, including the mixture of mercury's emission peaks, possible filter degradation, an inability to separate overlapping emission features, and the sensitivity and subjectivity of human vision and color interpretation. A multi-excitation photoluminescence (PL) spectroscopy system has been built for gemstone analysis, incorporating 261 and 405 nm laser excitations to study gemstone emission features between 270 to 1000 nm. This system presents significant improvements, extending the detection spectral range, increasing the sensitivity, accuracy and reproducibility of gemstone luminescence analysis. Luminescence analysis of commercially valuable gemstones are presented to demonstrate the system's suitability for gemstone identification. Examples include distinguishing natural from laboratory-grown diamonds, thermal and color treatment detection for corundum and pearls, respectively, and mineral type separation of emeralds and other green gemstones.