Raman Microspectroscopic Study of the Cation Distribution in Amphiboles

The first attempt to determine the cation distributions in amphiboles by Raman microspectroscopy is described. The Raman spectra of five amphibole samples were obtained. It was observed that the Raman bands of the OH stretching modes were narrower than the corresponding infrared bands previously reported. However, even with the use of the most sophisticated Raman instruments, It was not possible to distinguish the bands due to the different cation arrangements of one particular configuration. Nevertheless, the experimental results and the theoretical analysis developed here allowed approximate calculations of the site occupancies to be made for four samples. These results yield a better understanding of the problems involved in the determination of the cation distributions in amphiboles with the use of vibrational spectroscopic methods.