The effect of As-Sb substitution in the Raman spectra of tetrahedrite-tennantite and pyrargyrite-proustite solid solutions

Raman spectra of 17 fahlore samples (tetrahedrite-tennantite solid solution series) and 3 samples of the pyrargyrite-proustite solid solution series were recorded. The fundamental stretching and bending vibrations of the pyramidal (Sb, AS)S-3 groups occur between 200 and 400 cm(-1). The position, shape, relative intensity and appearance of the bands vary depending upon the Sb/(Sb+As) ratios of both mineral series. The symmetric stretching mode (v(1)) shows a two-mode behavior in the tetrahedrite-tennantite solid solution series, whereas one-mode behavior is observed in all other cases. The excellent correlations between the positions of the vibrational modes and the Sb/(Sb+As) ratio, can be applied to determine the composition of the investigated sample by at least one band in the Raman spectrum of the mineral.