Raman and infrared spectral studieswere performed on six natural minerals from the doublechain silicate group. We analyzed samples of grunerite, actinolite, tremolite, pargasite (+kaersutite) and riebeckite in order to determine the spectral differencesbetween them and to identify the vibrations that occur. Also, for one sample thought to be pargasitewe obtained the Raman spectrum of kaersutite, while anothersample was determined as a Ti-rich pargasite, since the difference between these two minerals consists in the presence of more than 0.50apfu ^VITi in kaersutite (titaniferous calcic amphibole). The Raman spectrum of kaersutite exhibits characteristic bands of the ^VITi-OH vibration around 580–590cm^-1 and 750cm^-1. These two bands are stronger than the symmetric stretching vibration of the Si-Ob-Si (ν1), which arisesas the strongest band in all otheramphibole minerals ofthe present study, around 650–670cm^-1. Both Raman and infrared spectra of all the analyzed samples reveal the presence of Fe²⁺, Mg²⁺ or other cations in the octahedral sites, displaying distinct bands in the ~300-450cm^-1 spectral region, as well as in the OH stretching region (3600–3700cm^-1).
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kaersutite, Ti-rich pargasite, amphiboles, Raman, infrared, Spectroscopy, OH^- stretching, double-chain silicates