Vibrational (infrared and raman) spectra of minerals and related compounds / Колебательные (инфракрасные и комбинационные) спектры минералов и родственных соединений

Vesuvianite-group minerals (VGM) are widespread and occur in different geological formations including regional metamorphic rocks, skarns, rodingites, etc. Specific crystal-chemical features of these minerals reflect conditions of their crystallization. As a rule, high-temperature VGM have high-symmetry structures (space group P4/ nnc), whereas low-temperature samples are characterized by the symmetry P4/n or P4nc (Allen and Burnham 1992). The simplified crystal-chemical formula of VGM is X18(X´Y1) Y24Y38T0–5(SiO4)10(Si2O7)4O1-2W9 where X, X´ ¼ Ca, Na, K, Fe2+, and REE (cations with coordination numbers from 7 to 9); Y1–Y3 ¼ Al, Mg, Fe2+, Fe3+, Mn2+, Mn3+, Ti, Cr, Сu, Zn; T ¼ B, Al, □; W ¼ OH, F, O. The Y1 cations have tetragonal-pyramidal coordination, whereas the Y2 and Y3 cations occur in octahedra. IR spectra of VGM are discussed in numerous publications (Paluszkiewicz and Żabiński 1992; Groat et al. 1995; Kurazhkovskaya and Borovikova 2003; Kurazhkovskaya et al. 2005; Borovikova and Kurazhkovskaya 2006); however, in most cases their interpretation is ambiguous. We have obtained IR spectra of 33 VGM samples from different kinds of localities which have been preliminarily investigated in detail using electron microprobe (including determination of boron), single-crystal X-ray structural analysis, DSC, 27Al NMR, ICP-MS, and Mössbauer spectroscopy. As a result, characteristic IR bands corresponding to different local situations in the structures of VGM have been revealed. Data on crystal structures, crystal chemistry, and IR spectra of these samples are published by Britvin et al. (2003), Panikorovskii et al. (2016a–d, 2017a–d), and Aksenov et al. (2016). The most important results of this investigation are listed below in comparison with data published elsewhere <...>