Raman spectroscopic study of the mineral gerstleyite Na 2 (Sb,As) 8 S 13 ·2H 2 O and comparison with some heavy‐metal sulfides

The mineral gerstleyite is described as a sulfosalt as opposed to a sulfide. This study focuses on the Raman spectrum of gerstleyite Na 2 (Sb,As) 8 S 13 ·2H 2 O and makes a comparison with the Raman spectra of other common sulfides including stibnite, cinnabar and realgar. The intense Raman bands of gerstleyite at 286 and 308 cm −1 are assigned to the SbS 3 E antisymmetric and A 1 symmetric stretching modes of the SbS 3 units. The band at 251 cm −1 is assigned to the bending mode of the SbS 3 units. The mineral stibnite also has basic structural units of Sb 2 S 3 and SbS 3 pyramids with C 3 v symmetry. Raman bands of stibnite Sb 2 S 3 at 250, 296, 372 and 448 cm −1 are assigned to SbS stretching vibrations and the bands at 145 and 188 cm −1 to SSbS bending modes. The Raman band for cinnabar HgS at 253 cm −1 fits well with the assignment of the band for gerstleyite at 251 cm −1 to the SSbS bending mode. Raman bands in similar positions are observed for realgar AsS and orpiment As 2 S 3 . Copyright © 2010 John Wiley & Sons, Ltd.