The amphibole group of minerals comprises a large number of species, some of which have typically fibrous shapes and are thus of interest for environmental hazard issues. Their identification is complicated by the presence of light elements (H and Li), multi-valence elements (e.g. Fe, Mn) and a partially vacant structural site. Vibrational spectroscopies are valuable tools to address the quantitative determination of occupancies in amphiboles: however, whilst Fourier-Transform Infra-Red Spectroscopy (FTIR) has been preferentially used in crystal-chemical studies, Raman spectroscopy has been restricted to asbestos identification. In this work we focus our attention on two sets of well-characterised synthetic amphiboles, i.e. on samples along the potassium-richterite − tremolite join, and the Na(NaMg)Mg5Si8O22(OH)2 compound synthesised at different T and P conditions. We show that the Raman spectra in the OH-stretching region are very similar, in terms of band shape and multiplicity to the FTIR spectra; however, the relative intensity of the Raman peaks provides direct quantitative information on the A-site occupancy, a feature that has significant implications as a tool for asbestos studies.
Quantifying the A-site occupancy in amphiboles: a Raman study in the OH-stretching region
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Marco Sbroscia, Giancarlo Della Ventura, Gianluca Iezzi, Armida Sodo; Quantifying the A-site occupancy in amphiboles: a Raman study in the OH-stretching region. European Journal of Mineralogy ; 30 (3): 429–436. doi: https://doi.org/10.1127/ejm/2018/0030-2727
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