Minerals From Macedonia. XXI. Vibrational Spectroscopy as Identificational Tool for Some Phyllosilicate Minerals

Vibrational (infrared and Raman) spectra of the sheet silicate minerals: biotite, K(Mg,Fe2+)3AlSiO10(OH,F)2; muscovite, KAl2(Si3Al)O10(OH,F)2; phlogopite, KMg3(Si3Al)O10(F,OH)2 and sheridanite (clinochlore), (Mg,Al)6(Si,Al)4O10(OH)8, collected from various localities within the Republic of Macedonia, were described and interpreted. The above-mentioned minerals showed IR spectral similarities in the region bellow 1200 cm–1 mainly due to their common structural characteristics. In general, the bands appearing in the 1100–900 cm–1 spectral region were assigned to v(Si–O–Si) modes, whereas most of the lower-frequency bands were interpreted as either s(OH) or s(Si–O–Si) vibrations. The similarities between the Raman spectra (1200-100 cm–1) were less pronounced indicating that Raman technique is more sensitive to compositional changes. The results were compared to the literature data for the analogous species originating from all over the world. The authenticity of the samples was checked by powder XRD and chemical composition determined by X-ray microprobe analysis.