A LASER RAMAN MICROPROBE STUDY OF SOME GEOLOGICALLY IMPORTANT SULFIDE MINERALS

Laser micro-Raman spectroscopy has been used to study 20 of the most commonly occurring sulphides (i.e. iron sulphides, copper sulphides and some sulphosalts) which cover many of the structural variations that occur in sulphide minerals. Most structures, including polymorphs, produced unique Raman spectra which can readily be used to identify and discriminate one mineral from another. A few sulphides, such as galena and pyrrhotite, do not exhibit a first-order Raman spectrum due to their structural symmetry, and Raman spectra could not be obtained from some of the metal-excess groups of sulphides because of their many metallic characteristics. However, good quality Raman spectra were obtained from most sulphides and sulphosalts examined in this study. The observed bands were compared with those predicted from theoretical analyses and also with spectra from similar minerals and are shown to be sensitive to structural and compositional order or disorder. Finally, the advantages and disadvantages of using this technique for certain geological applications are presented and discussed.