Standardless, minimally destructive chemical analysis of red beryls by means of Laser Induced Breakdown Spectroscopy

Abstract

Laser Induced Breakdown Spectroscopy (LIBS) is a valuable technique for performing qualitative and quantitative chemical analyses of all elements in one shot, including light elements (like Li and Be). This technique does not require any sample preparation and reveals all atomic species, even when present in small amounts. In this study we use a new LIBS prototype coupled with a petrographic microscope to obtain a spot size of approximately 10 μm on selected and homogeneous areas with minimal damage to the mineral. Qualitative and quantitative chemical analyses were performed on six samples of a rare red variety of beryl, using a standardless method (Calibration Free-LIBS) for quantitative data. Preliminary analyses by Raman spectroscopy and VIS-NIR reflectance spectroscopy showed that two of the six samples were pezzottaite. The LIBS spectra confirm the Raman and VIS-NIR data, demonstrating that this technique can distinguish red beryl from pezzottaite, mainly by observing the differences in Cs and Li emission lines. The standardless quantitative analysis proves to be suitable for the quantification of major and minor elements in beryl, as shown by comparison with literature data. In particular, the quantification of Mn confirmed a direct correlation between the concentration of this chromophore element and the red colour saturation of the samples.