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2026-06-11 23:58

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Conference: Bucharest University Faculty of Physics 2026 Meeting

Section: Atomic and Molecular Physics. Astrophysics. Applications. Optics, Spectroscopy, Plasma and Lasers

Title:

Multi-Analytical Characterization of Microcrystalline and Amorphous Silicates

Authors:

Andreea IONESCU(1,2), Cătălin-Romeo LUCULESCU(2), Doina BEJAN(1)

Affiliation:

1) Faculty of Physics, University of Bucharest, Atomiştilor Street 405, 077125 Măgurele, Ilfov, Romania

2) National Institute for Laser, Plasma and Radiation Physics (INFLPR), Atomiştilor Street 409, 077125 Măgurele, Ilfov, Romania

E-mail

andreea.ionescu3344@gmail.com

Keywords:

Raman spectroscopy, LIBS, SEM, EDS, silica, carnelian, obsidian, agate

Abstract:

The accurate identification and characterization of semi-precious stones and geological glasses demand advanced, non-destructive analytical frameworks [1] and while conventional gemological testing provides basic optical parameters, it often falls short in revealing the complex micro-chemical composition and structural history of silica-rich materials. In this study, we present a multi-instrumental methodology designed to investigate the structural, elemental, and morphological properties of three distinct geological matrices: carnelian, agate, and obsidian. In order to overcome the inherent limitations of individual techniques, molecular vibrational profiles were acquired using Raman microspectroscopy, while elemental emission lines and localized chemical quantification were determined by combining Laser-Induced Breakdown Spectroscopy (LIBS) and Scanning Electron Microscopy coupled with Energy-Dispersive X-Ray Spectroscopy (SEM-EDS). Raman analysis successfully differentiated the highly ordered microcrystalline aggregates of the chalcedonies, which confirmed the coexistence of α-quartz and moganite phases [2], from the disordered, metastable network of obsidian. LIBS proved exceptionally sensitive to trace elements, identifying specific chromophores such as iron and vanadium in the chalcedonies [3], alongside rare-earth magmatic markers including yttrium and titanium in the obsidian sample. On the other hand, high-vacuum SEM-EDS mapping corroborated the bulk aluminosilicate stoichiometry and surface topography [4]. However, EDS failed to detect the ultra-trace transition metals identified by the laser plasma, which signaled the necessity of LIBS for comprehensive geochemical fingerprinting. In conclusion, the results demonstrate that synergizing optical spectroscopy, laser-induced plasma emissions, and electron microscopy provides a robust, minimally destructive protocol for authenticating and characterizing complex geological materials.

References:

[1] Bersani D. & Lottici P. P. (2010). "Applications of Raman spectroscopy to gemology" Analytical and Bioanalytical Chemistry, 397(7), 2631-2646.

[2] Kingma K. J. & Hemley R. J. (1994). "Raman spectroscopic study of microcrystalline silica" American Mineralogist, 79(3-4), 269-273.

[3] Götze J., et al. (2001). "Geochemistry of agates: a trace element and stable isotope study" Chemical Geology, 175(3-4), 523-541.

[4] Goldstein J. I., et al. (2017). "Scanning Electron Microscopy and X-Ray Microanalysis (4th ed.)" Springer, 1-20.

Acknowledgement:

We acknowledge the support of the National Interest Infrastructure facility IOSIN—CETAL at INFLPR.