Raman spectroscopic investigations of some Tl-sulfosalt minerals containing pyramidal (As,Sb)S₃ groups

Oriented single crystals of stibioellisite (Tl₃SbS₃), parapierrotite (TlSb₅S₈), weissbergite (TlSbS₂), and lorandite (TlAsS₂) were investigated by polarized Raman spectroscopy. Whereas stibioellsite shows isolated SbS₃ groups, the rest of the minerals show interconnected pyramidal (As,Sb)S₃ groups. Raman bands of the investigated minerals occur between 400 and 10 cm⁻¹. The internal vibrations for stibioellsite occur between 350–100 cm⁻¹. Those of the interconnected pyramidal groups occur between 350 and 10 cm⁻¹ in parapierrotite, 350 and 90 cm⁻¹ in weissbergite, and 420 and 130 cm⁻¹ in lorandite. Approximate similarities in the spectral features are evident when comparing the spectra of minerals containing XS₃ pyramids with the spectra of the minerals in the present study. A clear distinction between Raman spectra of separated and interconnected SbS₃ groups is not observed.