Articles | Volume 37, issue 1
https://doi.org/10.5194/ejm-37-53-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/ejm-37-53-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
07 Feb 2025
Research article |
| 07 Feb 2025
| 07 Feb 2025
Fingerprinting of ruby and sapphire gemstones through Fourier-transform infrared (FTIR) methodologies
António Soares de Sousa
CORRESPONDING AUTHOR
Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona, Barcelona 08028, Spain
Elsa Maria Carvalho Gomes
Centre for Earth and Space Research of the University of Coimbra – CITEUC, Department of Earth Sciences, Faculty of Sciences and Technology, University of Coimbra, Rua Sílvio Lima, 3030-790 Coimbra, Portugal
Laura Bayés-García
Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona, Barcelona 08028, Spain
Alessandra Di Mariano
Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona, Barcelona 08028, Spain
Maite Garcia-Valles
Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona, Barcelona 08028, Spain
Related subject area
Spectroscopic methods applied to minerals
Mineralogical characterization of magnesium-based nanoparticles recovered from a swirl-stabilized magnesium flame by analytical and scanning/transmission electron microscopy
Laser-induced breakdown spectroscopy analysis of tourmaline: protocols, procedures, and predicaments
Near-infrared signature of hydrothermal opal: a case study of Icelandic silica sinters
Vibrational properties of OH groups associated with divalent cations in corundum (α-Al2O3)
The effect of chemical variability and weathering on Raman spectra of enargite and fahlore
OH incorporation and retention in eclogite-facies garnets from the Zermatt–Saas area (Switzerland) and their contribution to the deep water cycle
Optimal Raman-scattering signal for estimating the Fe3+ content on the clinozoisite–epidote join
A framework for quantitative in situ evaluation of coupled substitutions between H+ and trace elements in natural rutile
Effect of Fe–Fe interactions and X-site vacancy ordering on the OH-stretching spectrum of foitite
Molecular overtones and two-phonon combination bands in the near-infrared spectra of talc, brucite and lizardite
Non-destructive determination of the biotite crystal chemistry using Raman spectroscopy: how far we can go?
Crystallographic orientation mapping of lizardite serpentinite by Raman spectroscopy
The effect of Co substitution on the Raman spectra of pyrite: potential as an assaying tool
Theoretical OH stretching vibrations in dravite
First-principles modeling of the infrared spectrum of Fe- and Al-bearing lizardite
Structural, textural, and chemical controls on the OH stretching vibrations in serpentine-group minerals
The intracrystalline microstructure of Monte Fico lizardite, by optics, μ-Raman spectroscopy and TEM
First-principles modeling of the infrared spectrum of antigorite
A Raman spectroscopic study of the natural carbonophosphates Na3MCO3PO4 (M is Mn, Fe, and Mg)
Local mode interpretation of the OH overtone spectrum of 1:1 phyllosilicates
Low-temperature infrared spectrum and atomic-scale structure of hydrous defects in diopside
In situ micro-FTIR spectroscopic investigations of synthetic ammonium phengite under pressure and temperature
Theoretical infrared spectra of OH defects in corundum (α-Al2O3)
Ruggero Vigliaturo, Giulia Pia Servetto, Erica Bittarello, Quentin Wehrung, Jean-François Brilhac, and Gwenaëlle Trouvé
Eur. J. Mineral., 36, 831–843, https://doi.org/10.5194/ejm-36-831-2024, https://doi.org/10.5194/ejm-36-831-2024, 2024
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Technology for producing energy with zero-carbon emissions must be developed in light of the current climate emergency. Using recyclable metal fuels, such as magnesium (Mg), is one practical solution. Metals can therefore be seen as regenerable fuels and new energy vectors since the energy they contain can be transferred and released through metal combustion. To optimize the particle trapping capacity of the investigated system, we successfully characterized magnesium oxide (MgO) crystals.
Nancy J. McMillan and Barbara L. Dutrow
Eur. J. Mineral., 36, 369–379, https://doi.org/10.5194/ejm-36-369-2024, https://doi.org/10.5194/ejm-36-369-2024, 2024
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The mineral tourmaline records the geologic environment in which it crystallizes. Methods were developed for laser-induced breakdown spectroscopy analysis of tourmaline. Problems that were solved include the spacing between analysis locations to avoid the recast layer from previous analyses, the efficacy of using cleaning shots prior to data acquisition, the number of analyses needed to obtain a representative average analysis, and the effect of spectrometer drift on multivariate analysis.
Maxime Pineau, Boris Chauviré, and Benjamin Rondeau
Eur. J. Mineral., 35, 949–967, https://doi.org/10.5194/ejm-35-949-2023, https://doi.org/10.5194/ejm-35-949-2023, 2023
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We study Icelandic silica sinter samples formed in hot-spring environments to evaluate the effect of both temperature and microstructure on the spectral properties of hydrothermal opal. We show that spectral changes can be related to different parameters such as fluid temperatures, hydrodynamics, microbial activity, and silica micro-textures, which are specific to their environment of formation within hot-spring geothermal contexts.
Michael C. Jollands, Shiyun Jin, Martial Curti, Maxime Guillaumet, Keevin Béneut, Paola Giura, and Etienne Balan
Eur. J. Mineral., 35, 873–890, https://doi.org/10.5194/ejm-35-873-2023, https://doi.org/10.5194/ejm-35-873-2023, 2023
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The infrared spectrum of hydrous defects in corundum is routinely used in gemology, but the assignment of absorption bands to specific defects remains elusive. Here, we theoretically study selected defects and compare the results with available experimental data. The main results are the assignment of the
3161 cm−1 seriesto OH groups associated with Fe2+ ions and the interpretation of bands below 2700 cm−1 in corundum containing divalent cations in terms of overtones of OH bending modes.
Khulan Berkh, Juraj Majzlan, Jeannet A. Meima, Jakub Plášil, and Dieter Rammlmair
Eur. J. Mineral., 35, 737–754, https://doi.org/10.5194/ejm-35-737-2023, https://doi.org/10.5194/ejm-35-737-2023, 2023
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Since As is detrimental to the environment, the As content of ores should be reduced before it is released into the atmosphere through a smelting process. Thus, Raman spectra of typical As minerals were investigated, and these can be used in the industrial removal of As-rich ores prior to the ore beneficiation. An additional objective of our study was an investigation of the secondary products of enargite weathering. They play a decisive role in the release or retainment of As in the waste form.
Julien Reynes, Jörg Hermann, Pierre Lanari, and Thomas Bovay
Eur. J. Mineral., 35, 679–701, https://doi.org/10.5194/ejm-35-679-2023, https://doi.org/10.5194/ejm-35-679-2023, 2023
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Garnet is a high-pressure mineral that may incorporate very small amounts of water in its structure (tens to hundreds of micrograms per gram H2O). In this study, we show, based on analysis and modelling, that it can transport up to several hundred micrograms per gram of H2O at depths over 80 km in a subduction zone. The analysis of garnet from the various rock types present in a subducted slab allowed us to estimate the contribution of garnet in the deep cycling of water in the earth.
Mariko Nagashima and Boriana Mihailova
Eur. J. Mineral., 35, 267–283, https://doi.org/10.5194/ejm-35-267-2023, https://doi.org/10.5194/ejm-35-267-2023, 2023
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We provide a tool for fast preparation-free estimation of the Fe3+ content in Al–Fe3+ series epidotes by Raman spectroscopy. The peaks near 570, 600, and 1090 cm−1, originating from Si2O7 vibrations, strongly correlated with Fe content, and all three signals are well resolved in a random orientation. Among them, the 570 cm−1 peak is the sharpest and easily recognized. Hence, the linear trend, ω570 = 577.1(3) − 12.7(4)x, gives highly reliable Fe content, x, with accuracy ± 0.04 Fe3+ apfu.
Mona Lueder, Renée Tamblyn, and Jörg Hermann
Eur. J. Mineral., 35, 243–265, https://doi.org/10.5194/ejm-35-243-2023, https://doi.org/10.5194/ejm-35-243-2023, 2023
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Although rutile does not have water in its chemical formula, it can contain trace amounts. We applied a new measurement protocol to study water incorporation into rutile from eight geological environments. H2O in natural rutile can be linked to six crystal defects, most importantly to Ti3+ and Fe3+. Quantifying the H2O in the individual defects can help us understand relationships of trace elements in rutile and might give us valuable information on the conditions under which the rock formed.
Etienne Balan, Guillaume Radtke, Chloé Fourdrin, Lorenzo Paulatto, Heinrich A. Horn, and Yves Fuchs
Eur. J. Mineral., 35, 105–116, https://doi.org/10.5194/ejm-35-105-2023, https://doi.org/10.5194/ejm-35-105-2023, 2023
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Assignment of OH-stretching bands to specific atomic-scale environments in tourmaline is still debated, which motivates detailed theoretical studies of their vibrational properties. We have theoretically investigated the OH-stretching spectrum of foitite, showing that specific OH bands observed in the vibrational spectra of iron-rich and Na-deficient tourmalines are affected by the magnetic configuration of iron ions and X-site vacancy ordering.
Etienne Balan, Lorenzo Paulatto, Qianyu Deng, Keevin Béneut, Maxime Guillaumet, and Benoît Baptiste
Eur. J. Mineral., 34, 627–643, https://doi.org/10.5194/ejm-34-627-2022, https://doi.org/10.5194/ejm-34-627-2022, 2022
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The near-infrared spectra of hydrous minerals involve OH stretching vibrations, but their interpretation is not straightforward due to anharmonicity and vibrational coupling. We analyze the spectra of well-ordered samples of talc, brucite and lizardite to better assess the various factors contributing to the absorption bands. The results clarify the relations between the overtone spectra and their fundamental counterparts and provide a sound interpretation of the two-phonon combination bands.
Stylianos Aspiotis, Jochen Schlüter, Günther J. Redhammer, and Boriana Mihailova
Eur. J. Mineral., 34, 573–590, https://doi.org/10.5194/ejm-34-573-2022, https://doi.org/10.5194/ejm-34-573-2022, 2022
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Combined Raman-scattering and wavelength-dispersive electron microprobe (WD-EMP) analyses of natural biotites expanding over the whole biotite solid-solution series demonstrate that the chemical composition of the MO6 octahedra, TO4 tetrahedra, and interlayer space can be non-destructively determined by Raman spectroscopy with relative uncertainties below 8 %. The content of critical minor elements such as Ti at the octahedral site can be quantified as well with a relative error of ~ 20 %.
Matthew S. Tarling, Matteo Demurtas, Steven A. F. Smith, Jeremy S. Rooney, Marianne Negrini, Cecilia Viti, Jasmine R. Petriglieri, and Keith C. Gordon
Eur. J. Mineral., 34, 285–300, https://doi.org/10.5194/ejm-34-285-2022, https://doi.org/10.5194/ejm-34-285-2022, 2022
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Rocks containing the serpentine mineral lizardite occur in many tectonic settings. Knowing the crystal orientation of lizardite in these rocks tells us how they deform and gives insights into their physical properties. The crystal orientation of lizardite is challenging to obtain using standard techniques. To overcome this challenge, we developed a method using Raman spectroscopy to map the crystal orientation of lizardite with minimal preparation on standard thin sections.
Khulan Berkh and Dieter Rammlmair
Eur. J. Mineral., 34, 259–274, https://doi.org/10.5194/ejm-34-259-2022, https://doi.org/10.5194/ejm-34-259-2022, 2022
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Common energy dispersive methods cannot accurately analyze low concentrations of cobalt in pyrite due to the overlapping of cobalt and iron peaks. The Raman method, on the other hand, has been shown to be very sensitive to a trace amount of cobalt. In addition, it can be applied on a rough surface, does not require a vacuum chamber, and operates with a laser instead of X-rays. Thus, Raman has the potential to be used as an assaying tool for Co-bearing pyrite.
Yves Fuchs, Chloé Fourdrin, and Etienne Balan
Eur. J. Mineral., 34, 239–251, https://doi.org/10.5194/ejm-34-239-2022, https://doi.org/10.5194/ejm-34-239-2022, 2022
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Information about the local structure of tourmaline-group minerals can be obtained from the characteristic OH stretching bands in their vibrational spectra. However, their assignment to specific atomic-scale environments is debated. We address this question theoretically by investigating a series of dravite models. Our results support a local role of cationic occupancies in determining the OH stretching frequencies and bring constraints for the interpretation of the vibrational spectra.
Etienne Balan, Emmanuel Fritsch, Guillaume Radtke, Lorenzo Paulatto, Farid Juillot, Fabien Baron, and Sabine Petit
Eur. J. Mineral., 33, 647–657, https://doi.org/10.5194/ejm-33-647-2021, https://doi.org/10.5194/ejm-33-647-2021, 2021
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Interpretation of vibrational spectra of serpentines is complexified by the common occurrence of divalent and trivalent cationic impurities at tetrahedral and octahedral sites. We theoretically investigate the effect of Fe and Al on the vibrational properties of lizardite, focusing on the OH stretching modes. The results allow us to disentangle the specific effects related to the valence and coordination states of the impurities, supporting a detailed interpretation of the experimental spectra.
Emmanuel Fritsch, Etienne Balan, Sabine Petit, and Farid Juillot
Eur. J. Mineral., 33, 447–462, https://doi.org/10.5194/ejm-33-447-2021, https://doi.org/10.5194/ejm-33-447-2021, 2021
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The study provides new insights into the OH stretching vibrations of serpentine species (lizardite, chrysotile, antigorite) encountered in veins of peridotite. A combination of infrared spectroscopy in the mid-infrared and near-infrared ranges and Raman spectroscopy enabled us to interpret most of the observed bands in the fundamental and first overtone regions of the spectra and to propose consistent spectral decomposition and assignment of the OH stretching bands for the serpentine species.
Giancarlo Capitani, Roberto Compagnoni, Roberto Cossio, Serena Botta, and Marcello Mellini
Eur. J. Mineral., 33, 425–432, https://doi.org/10.5194/ejm-33-425-2021, https://doi.org/10.5194/ejm-33-425-2021, 2021
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Unusually large lizardite (Lz) crystals from Monte Fico serpentinites, Elba (Mellini and Viti, 1994), have allowed several subsequent studies. During a µ-Raman study of serpentine minerals (Compagnoni et al., 2021), the careful microscopic examination of this Lz showed
spongymicrostructure. TEM observations confirmed that the Lz hosts voids, filled with chrysotile and polygonal serpentine; their mutual relationships indicate that Lz grew up with a skeletal habit and fibres epitactically.
Etienne Balan, Emmanuel Fritsch, Guillaume Radtke, Lorenzo Paulatto, Farid Juillot, and Sabine Petit
Eur. J. Mineral., 33, 389–400, https://doi.org/10.5194/ejm-33-389-2021, https://doi.org/10.5194/ejm-33-389-2021, 2021
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The infrared absorption spectrum of an antigorite sample, an important serpentine-group mineral, is compared to its theoretical counterpart computed at the density functional level. The model reproduces most of the observed bands, supporting their assignment to specific vibrational modes. The results provide robust interpretations of the significant differences observed between the antigorite spectrum and that of lizardite, the more symmetric serpentine variety.
Evgeniy Nikolaevich Kozlov, Ekaterina Nikolaevna Fomina, Vladimir Nikolaevich Bocharov, Mikhail Yurievich Sidorov, Natalia Sergeevna Vlasenko, and Vladimir Vladimirovich Shilovskikh
Eur. J. Mineral., 33, 283–297, https://doi.org/10.5194/ejm-33-283-2021, https://doi.org/10.5194/ejm-33-283-2021, 2021
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Carbonophosphates (sidorenkite, bonshtedtite, and bradleyite) with the general formula Na3MCO3PO4 (M is Mn, Fe, and Mg) are often found in inclusions of carbonatite and kimberlite minerals. This article presents the results of Raman spectroscopic study and a simple algorithm for diagnosing mineral phases of the carbonophosphate group. This work may be of interest both to researchers of carbonatites and/or kimberlites and to a wide range of specialists in the field of Raman spectroscopy.
Etienne Balan, Emmanuel Fritsch, Farid Juillot, Thierry Allard, and Sabine Petit
Eur. J. Mineral., 33, 209–220, https://doi.org/10.5194/ejm-33-209-2021, https://doi.org/10.5194/ejm-33-209-2021, 2021
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The OH overtone bands of kaolinite- and serpentine-group minerals observed in their near-infrared (NIR) spectra are widely used but their relation to stretching modes involving coupled OH groups is uncertain. Here, we map a molecular model of harmonically coupled anharmonic oscillators on the spectroscopic properties of 1:1 phyllosilicates. This makes it possible to interpret most of the observed bands and support the assignment of some of them to cationic substitutions in serpentines.
Etienne Balan, Lorenzo Paulatto, Jia Liu, and Jannick Ingrin
Eur. J. Mineral., 32, 505–520, https://doi.org/10.5194/ejm-32-505-2020, https://doi.org/10.5194/ejm-32-505-2020, 2020
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The atomic-scale geometry of hydrous defects in diopside is still imperfectly known despite their contribution to the Earth's water cycle. Their OH-stretching vibrations lead to a variety of infrared absorption bands. Low-temperature infrared spectroscopy makes it possible to resolve additional bands in the spectra of gem-quality natural samples. Theoretical results obtained at the density functional theory level support the assignment of the observed bands to specific atomic-scale models.
Nada Abdel-Hak, Bernd Wunder, Ilias Efthimiopoulos, and Monika Koch-Müller
Eur. J. Mineral., 32, 469–482, https://doi.org/10.5194/ejm-32-469-2020, https://doi.org/10.5194/ejm-32-469-2020, 2020
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The structural response of the NH4+ molecule to temperature and pressure changes is studied in ammonium phengite. The symmetry of the molecule is lowered by increasing P or decreasing T; the type and mechanism of this lowered symmetry is different in both cases. Devolatilisation (NH4+ and OH loss) of ammonium phengite is studied as well. This study confirms the wide stability range of phengite and its volatiles and thus has important implications for N and H recycling into the deep Earth.
Etienne Balan
Eur. J. Mineral., 32, 457–467, https://doi.org/10.5194/ejm-32-457-2020, https://doi.org/10.5194/ejm-32-457-2020, 2020
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Corundum is an important oxide mineral which can contain low amounts of hydrogen-bearing structural defects. These defects are observed by infrared spectroscopy, but their atomic-scale geometry is still uncertain. Here, a theoretical approach makes it possible to relate most of the observed infrared bands to specific atomic configurations, highlighting the key role of other chemical impurities and defect clustering in the high-temperature incorporation of hydrogen in corundum.
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Short summary
In this work, we used Fourier-transform infrared (FTIR) spectroscopy to analyse 25 rubies and sapphires, including natural, synthetic, and treated specimens. By optimising sample positioning, we identified distinct spectral fingerprints for each type and treatment. This systematic approach enhances gemstone identification accuracy and contributes valuable data to existing gemological databases, enabling faster and more reliable analyses in the future.
In this work, we used Fourier-transform infrared (FTIR) spectroscopy to analyse 25 rubies and...
