Minerals from Macedonia XIII: Vibrational spectra of some commonly appearing nesosilicate minerals

The vibrational (infrared and Raman) spectra of seven common nesosilicate minerals [almandine, Fe3Al2(SiO4)3; spessartine, Mn3Al2(SiO4)3; zircon, ZrSiO4; titanite, CaTiOSiO4; olivine, (Mg,Fe)2SiO4; kyanite, Al2OSiO4 and staurolite, Fe2Al9O6(SiO4)4(OH)2] in the region from 1200 to 370 cm−1 (infrared, for staurolite from 3750 to 3250 cm−1, as well) and from 1200 to 100 cm−1 (Raman) are studied. The observed spectral behavior is discussed in terms of the structural characteristics of orthosilicates (nesosilicates) where no oxygen atoms are shared between the adjacent SiO4 tetrahedra. In spite of some differences, in general, rather expressed similarity among the infrared spectra of the minerals are observed in the region below 1200 cm−1, mainly due to their common structural characteristics. The similarity is especially expressed in the case of the isomorphous almandine and spessartine garnets, which form solid solution. Except staurolite, all mentioned minerals are nominally anhydrous and do not contain OH groups. The similarity between the Raman spectra of the studied minerals is less expressed compared to the IR analogues. The vibrational spectra of the studied mineral samples are compared with the corresponding literature data for the analogous mineral species originating all over the world and used for mineral identification.