Micro-Raman spectroscopy of selected Mo minerals from Su Seinargiu (Sardinia, Italy)

Raman spectra of selected molybdenum minerals, represented both by bismuth-molybdenum oxides (sardignaite, gelosaite, and mambertiite) and by molybdates [tancaite-(Ce), ichnusaite, nuragheite, and suseinargiuite] from the Su Seinargiu Mo-Bi prospect (Sardinia, Italy) are reported. Raman spectra were collected using samples previously characterized through X-ray diffraction and electron-microprobe analyses. Bismuth-molybdenum oxides are mainly characterized by bands in the range between 300 and 1000 cm-1, related to stretching modes of Mo-O and to Bi-O bonds. Bands related to O-H stretching modes were observed in the range between 3000 and 4000 cm-1. Raman spectra of molybdates are characterized by the four fundamental modes of MoO4 groups occurring between 250 and 1000 cm-1. Additionally, stretching bands related to O-H bonds were observed in tancaite-(Ce). Micro-Raman spectroscopy is an efficient tool for the discrimination of these rare phases, with some exceptions discussed in the text.