The effect of Co substitution on the Raman spectra of pyrite: potential as an assaying tool

Abstract

Abstract. The textural appearance of Co-bearing pyrite was visualized by a mapping method using a Raman microprobe. Two out of five Raman active modes (Eg and Ag) of pyrite were evaluated here. The obtained Raman map tightly correlates with a Co distribution map revealed by electron microprobe. Both Eg and Ag modes gradually downshift and broaden with increasing Co concentration. The broadening and shifting of the Ag mode is stronger compared to the Eg mode. Especially the intensity of the Ag mode drastically drops and diminishes in comparison to the Eg mode. Both 532 and 633 nm lasers revealed the same variation in position and width of the Eg and Ag modes. Only the intensity ratio of the modes differed because of an energy-dependent resonance scattering from the Ag mode. The 1064 nm laser was unsuitable since the Raman scattering intensity is inversely proportional to wavelength. Furthermore, highly broadened Raman modes at upshifted frequencies caused by the standard mechanical polishing could be avoided by analyzing cut or polished samples with a broad ion beam.