Abstract
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.
Highlights
Gem-quality minerals have been very significant throughout human history
The samples were analyzed based on some characteristic physical properties
The served spectral signatures elements theeach different samples and their corresponding observed spectral signatures of elements in the different samples and their corresponding wavelengths are summarized in Table 2 together with an elemental assignment
Summary
Gem-quality minerals have been very significant throughout human history. Due to desirable attributes of beauty, rarity, durability, and portability, as well as the transient appeal of fashion, gemstones have attained a valuable status in human life. Due to these factors, the provenance of gemstones is a widely discussed topic for geologists, historians, gemmologists, and others in the gem industry. The identification and characterization of minerals/materials is important from an analytical point of view. Mineralogists, petrologists, and gemmologists use a wide range of simple to sophisticated methods to identify and characterize minerals [1,2]. Gemstones can be characterized by several analytical methods. The characterization of gemstones is generally performed using different methods like the measurement of the index of refraction [3], UV–visible spectroscopy [4], analysis of fluid and mineral inclusions [5], infrared and Raman spectroscopy [6], and the characterization of crystallographic
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