Rapid Analysis of Chemical Composition and Physical Properties of Gemstones Using LIBS and Chemometric Technique

Featured Application Laser-induced breakdown spectroscopy is applied to a variety of gemstones for classification and characterization purposes. Laser-induced breakdown spectroscopy (LIBS), accompanied by chemometric data analysis, is used to identify and classify gemstones of various hardness. The study involves several gemstones: amethyst, aquamarine beryl, bloodstone citrine, diopside, and enstatite. Their hardness is determined through a correlation utilizing the spectral intensity ratio of the ionic to atomic spectral lines of an identified element in the LIB spectrum. The result of the relative hardness obtained from the LIBS analysis is in good agreement with the hardness measured from Mohs's scale of hardness, a popular qualitative method to determine hardness. In this work, a linear relationship has been established between the Mohs's hardness and the plasma excitation temperature. Thus, the hardness of the gemstones can be determined with the help of plasma excitation temperature. Moreover, the analysis of trace elements in LIB spectral data reveals that a particular element is responsible for the colors of gemstones. Therefore, the relative concentration of constituents is calculated for all gemstones and compared. Principal component analysis (PCA) is successfully applied to all gemstone spectra for rapid classification and discrimination based on their variable elemental concentrations and respective hardness.

Automated summary

The study utilizes laser-induced breakdown spectroscopy (LIBS) and chemometric data analysis to determine the hardness and color sources of gemstones. The relative hardness is determined through correlation and a linear relationship between hardness and plasma excitation temperature is established. Comparing the relative concentration of constituents of gemstones and applying principal component analysis (PCA) allows for rapid classification and discrimination based on variable elemental concentrations and respective hardness.