Spectroscopic characterization of natural chrysotile

Abstract

Chrysotile, a variety of serpentine mineral was investigated by vibrational and magnetic resonance spectroscopic methods. The SEM photograph of the sample shows that chrysotile is made up of thin and flexible fibrils, classified as asbestos. The calculated lattice parameters were a = 5.1961 ± 0.0053 Å, b = 9.2365 ± 0.0107 Å, c = 14.6208 ± 0.0039 Å; β = 90.15 ± 0.19°; Z = 4, with space group C2/ m. Three bands observed in the highest wavenumber region (3689 and 3648 cm −1) originate from the stretching vibrations of the two crystallographically different OH groups. The Raman spectrum shows bending vibrations of the SiO 4 tetrahedra at 390 and 348 cm −1. Substitution of the Si ions in SiO 4 tetrahedra by Al ions leads to low-field shifts in the 29Si NMR spectrum and the resonance line corresponding to Q 3 (1 Al) was observed at −89 ppm. This result was supported by the resonance line at ≈57 ppm in 27Al NMR spectrum.