SPECTROSCOPIC FINGERPRINTING OF FLUORESCENT GEMS

Visible light and near infrared spectroscopy (Vis-NIR) has only recently been used for gemological practices. In the past, it has been used to fingerprint multiple gemstones within the same species. To expand this area of study, 65 gems of various species (e.g., diamonds, spinels, emeralds, rubies…) were tested using Vis-NIR spectroscopy to collect and analyze the fluorescent spectra of these gems. Fluorescence was achieved through excitement of the gems with a 404 nm blue laser. What was found was slight differences in the placement of essential peaks within each gem’s spectra. For example, a diamond’s placement of the 450 nm peak may differ by up to 5 nm from another diamond’s peak. By using the non-metric multidimensional scaling function of RStudio, a statistical data analyzing tool, I was able to calculate a formula which assigns each gem a unique number. This number, which in turn, yields a fingerprinting technique to identify species of gems from one another. In addition, this technique can also help define gems so that individual gems of the same species can be told apart. Extra groupings found within the same species may be due to location differences. Due to the inherent risk that gemologists face with stolen stones, this method creates a way to network between jewelers and laboratories alike to increase the chances stolen gems, if recovered, could be identified.