Minerals from Macedonia

The vibrational spectroscopy is used in order to identify and characterize three sorosilicate minerals originating from the localities in the Republic of Macedonia: epidote, Ca2Al2(Fe3+,Al)(SiO4)(Si2O7)O(OH), hemimorphite, Zn4(Si2O7)(OH)2·H2O and ilvaite, CaFe22+Fe3+(Si2O7)O(OH). The chemical composition of these minerals is not necessarily fixed, especially for epidote-clinozoisite mineral series: Ca2Al2(Fe3+,Al)(SiO4)(Si2O7)O(OH)-Ca2Al2Al(SiO4)(Si2O7)O(OH), where the content of Fe3+ and Al could substantially vary. In this context, it was shown that the intensity and especially the frequency of the IR band in the ν(OH) region could serve as a tool for reliable determination of the Fe3+ and/or Al3+ in epidote. The similarity between the sorosilicate infrared spectra in the 1300-370 cm−1 region is based on their common structural characteristics. The bands in this region are tentatively assigned being mostly prescribed to the vibrations of the Si2O7 units (and SiO4 tetrahedra in epidote). On the other hand, the similarities between their Raman spectra are less expressed, especially in the case of ilvaite spectrum. The authenticity of the studied minerals is checked by the powder X-ray diffraction. The results of the study are compared with the corresponding literature data for the analogous mineral species originating all over the world.