Investigations of the Fe sulfosalts berthierite, garavellite, arsenopyrite and gudmundite by Raman spectroscopy

Arsenopyrite (FeAsS), gudmundite (FeSbS) and the rarer Fe sulfosalts berthierite (FeSb₂S₄) and garavellite (FeSbBiS₄), were investigated by Raman spectroscopy. Whereas (Sb, Bi)S₃ pyramids are responsible for the Raman spectra of berthierite and garavellite, the spectra of gudmundite and arsenopyrite arise from the stretching and bending modes of (Sb, As)S units. Internal vibrations for berthierite and garavellite occur between 400 and 50 cm^–1, and those of the gudmundite and arsenopyrite between 500 and 100 cm^–1. The longer bond distances of the SbS₃ groups readily explain the lower frequencies for berthierite in comparison with garavellite. Similarly, the greater mass and the longer bond distances of the Sb–S units also explain the lower frequencies observed for gudmundite relative to arsenopyrite.