In recent years, the use of Raman spectroscopy as a gemological tool has largely increased, in particular in the conservation science field where a non-destructive and contactless identification is required. In this work, we show the large amount of information which is possible to obtain with Raman analysis on one of the most important gems, emerald, the green variety of beryl. In particular, 14 not certified faceted emeralds have been studied by means of a standard micro-Raman spectrometer, allowing also the identification of some fakes (garnet, glass, and quartz). All the emerald gems have been fully characterized from the vibrational point of view. In particular, the high frequency spectrum, in the OH region, has been exploited to estimate the amount of alkali ions present in the channels of the crystalline structure. In addition, solid and fluid inclusions have been identified and were useful to hypothesize the provenance of the mineral. The shape and position of the characteristic laser-induced luminescence of chromium ions have helped to better define the origin of the gems

Albite is one of the most common minerals in the Earth's crust, and its polymorphs can be found in rocks with different cooling histories. The characteristic spectrum of vibration of the albite mineral reflects its structural Si/Al ordering. In this study, we report on the comparison between the Raman spectra measured on a natural and fully ordered (as deduced on the basis of single‐crystal X‐ray diffraction data) ‘low albite’, NaAlSi3O8, and those calculated at the hybrid Hartree–Fock/density functional theory level by employing the WC1LYP Hamiltonian, which has proven to give excellent agreement between calculated and experimentally measured vibrational wavenumbers in silicate minerals. All the 39 expected Ag modes are identified in the Raman spectra, and their wavenumbers and intensities, in different scattering configurations, correspond well to the calculated ones. The average absolute discrepancy |trueboldΔboldv¯| is ~3.4 cm−1, being the maximum discrepancy |Δv|max ~ 10.3 cm−1. The very good quality of the WC1LYP results allows for reliable assignments of the Raman features to specific patterns of atomic vibrational motion. Copyright © 2015 John Wiley & Sons, Ltd.

The Raman spectra of Ge‐clinopyroxenes CaM2+Ge2O6 (M2+ = Mg, Mn, Fe, Co, Ni, Zn), general formula M2M1T2O6, are reported for the first time. Their spectral features are discussed in comparison with corresponding Si‐pyroxenes. The vibrational wavenumbers of germanates may be roughly obtained by a scale factor of about ~0.8 by those of the corresponding silicates, due to the Ge‐Si mass difference. The main peaks in the germanate Raman spectra at ~850 and ~540 cm−1 may be related to Ge‐O tetrahedral stretching and chain bending, respectively; minor peaks between 200 and 400 cm−1 are ascribed to bending and stretching of the non‐tetrahedral cations. Within Ge‐pyroxenes, possible correlations between crystallographic parameters and the vibrational wavenumbers are investigated. The main stretching mode at ~850 cm−1 shows wavenumber changes with M2+ substitutions, but no simple correlation can be found with M2+ cation mass or size. On the other hand, the chain bending wavenumber linearly decreases with increasing ionic radius of the M2+ cation: the expansion of the M1 polyhedron reduces the chain kinking angle and the Ge‐Ge distances correspondingly increase. Copyright © 2015 John Wiley & Sons, Ltd.

configurations which affect the short range interactions and therefore the Raman frequencies.

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