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

Violeta Šontevska,^a Gligor Jovanovski,^a,b,* Petre Makreski,^a Aleksandra Raškovska^a and Bojan Šoptrajanov^a,b

^a Institute of Chemistry, Faculty of Science, Ss Cyril and Methodius University, Arhimedova 5, P.O. Box 162, 1001 Skopje, Republic of Macedonia
^b Macedonian Academy of Sciences and Arts, Bul. Krste Misirkov 2, P.O. Box 428, MK-1001 Skopje, Republic of Macedonia
* Corresponding author: E-mail: gligor@iunona.pmf.ukim.edu.mk

Abstract
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 ν(Si–O–Si) modes, whereas most of the lower-frequency bands were interpreted as either δ(OH) or δ(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.

Keywords: Vibrational spectroscopy, mica, identification, phyllosilicates.