The analysis of natural gemstones and their synthetic counterparts using analytical spectroscopy methods

Prompted by the increasing number, sophistication and quality of laboratory-grown gemstones; gemology has evolved into an individual science, incorporating the likes of biology and chemistry into its discipline. Synthetic gem materials are commonly encountered today in the jewellery industry and are becoming increasingly difficult to distinguish from their natural counterparts. A new approach is needed towards identification as traditional methods have shown to produce inconclusive results. The focus of this research is directed to some of the major commercial gemstones; ruby, sapphire, emerald and spinel to ensure the integrity of the international gemstone market.Raman spectroscopy makes for a useful analytical tool for the study of gemstones as it requires a small amount of material and short measurement times, no sample preparation and is non-destructive. For this work, a review of a laboratory Raman spectrometer equipped with 532nm and 780nm lasers respectively, and a portable Raman system with a 785nm laser applied in the gemology field is provided. Many examples are given of the use of Raman spectroscopy as an identification tool; primarily focussing on natural versus synthetic gems and the various types of synthetics produced using different manufacturing methods. Repetitive measurements conducted under an identical instrumental operation confirm the reliability of the results as Raman bands are found at correct wavenumber positions within a ±5cm-1 parameter compared to reference values in literature.Results of the laboratory Raman spectrometer show the instrument is capable of origin determination of gems of the same colour and for differentiating between natural and synthetic gemstones. A choice of two lasers proved useful as emerald analysis was only possible with the 532nm laser.The portable Raman system was able to distinguish between the different types of stones; however it proved less sensitive than the laboratory instrument as it could not distinguish between natural and synthetic gemstones