Micro‐Raman spectroscopic investigations of extremely scarce Pb–As sulfosalt minerals: baumhauerite,dufrénoysite,gratonite, sartorite,and seligmannite

The overmuch rare lead arsenic sulfosalts, baumhauerite (Pb₃As₄S₉), dufrénoysite (Pb₂As₂S₅), gratonite (Pb₉As₄S₁₅), sartorite (PbAs₂S₄), and seligmannite (PbCuAsS₃), were investigated by Raman spectroscopy. Raman spectra of the investigated minerals arise from the stretching and bending modes of the isolated and interconnected AsS₃ pyramidal groups. The As–S stretching vibrations of the studied minerals occur between 390 and 340 cm⁻¹, whereas those of S–As–S bending modes between 335 and 220 cm⁻¹. The shorter bond distances of the As–S readily elucidate the blue shift from seligmannite to gratonite, sartorite, dufrénoysite, and baumhauerite and the increase in full width at half maximum in similar modes. Copyright © 2016 John Wiley & Sons, Ltd.