Minerals from Macedonia. XVI. Vibrational spectra of some common appearing pyroxenes and pyroxenoids

✍ Scribed by Petre Makreski; Gligor Jovanovski; Andreja Gajović; Tomislav Biljan; Dejan Angelovski; Radojko Jaćimović

• Publisher: Elsevier Science
• Year: 2006
• Tongue: English
• Weight: 241 KB
• Volume: 788
• Category: Article
• ISSN: 0022-2860
• DOI: 10.1016/j.molstruc.2005.11.024

✦ Synopsis

Vibrational spectra of three pyroxenes: augite, (Ca,Na)(Mg,Fe,Mn,Al)(Si,Al) 2 O 6 , ferrojohannsenite, Ca(Fe,Mn)Si 2 O 6 and carpholite, MnAl 2 Si 2 O 6 (OH) 4 as well as two pyroxenoids: rhodonite, (Mn,Ca)MnSi 2 O 6 and bustamite, (Ca,Mn,Fe) 3 Si 3 O 9 were described and interpreted. The spectral behaviour was discussed in terms of their common structural characteristics since the pyroxenoids differ from pyroxenes by having distorted or twisted tetrahedral SiO 4 chains. It results with the subtle differences in the IR spectra mostly pronounced in the 800-650 cm K1 region. The bands in this region could serve as an indication about the number of the tetrahedra in repeating unit. The existence of the Raman counterparts of the IR bands (so called IR-Raman doublets) were observed although the centre of inversion is present in the structures of the minerals. It was explained by the existence of TOT I-strips in the structures whose stacking sequence symmetry dominates over the crystal symmetry and determines the symmetry and the activity of the normal modes.