Raman spectroscopy of the nickel silicate mineral pecoraite –an anologue of chrysotile (asbestos)

Abstract

The molecular structure of the mineral pecoraite, the nickel analogue of chrysotile of formula Ni3Si2O5(OH)4 has been analysed by a combination of Raman and infrared spectroscopy. A comparison is made with the spectra of the minerals nepouite and chrysotile and a synthetic pecoraite. Pecoraite is characterised by OH stretching vibrations at 3645 and 3683 cm-1 attributed to the inner and inner surface hydroxyl stretching vibrations. Intense infrared bands at around 3288 and 3425 cm-1 are assigned to the stretching vibrations of water strongly hydrogen bonded to the surface of the pecoraite. The asbestos-like mineral is charactersied by SiO stretching vibrations at 979, 1075, 1128, 1384 cm-1, OSiO chain vibrations at 616 and 761 cm-1 and Ni-O(H) vibrations at 397 and 451 cm-1.