RAMAN MICROPROBE SPECTROSCOPY OF HALLOYSITE

The Raman spectra of a tubular halloysite originating from Matauri Bay , New Zealand, have been obtained using a Renishaw 1000 Raman microsco pe system. The Raman microprobe enables the Raman spectra of crystals as small as 0.8 mu m diameter to be obtained over the complete wavelen gth range and allows spectral variations along the different crystal a xes to be studied. Three bands in the hydroxyl stretching region were observed at 3616.5, 3623.4 and 3629.7 cm(-1) and are attributed to the inner hydroxyls of the shared lower plane of the octahedral sheet of the halloysite. Two bands at 3698.2 and 3705 cm(-1) were obtained for the outer hydroxyls of the unshared outer octahedral plane. The relati ve intensity of the 3629.7 cm(-1) band varied according to the tube or ientation. Lattice vibrations of the halloysite were also found to be orientation-dependent.