Raman spectroscopy of the molybdate minerals chillagite (tungsteinian wulfenite-I4), stolzite, scheelite, wolframite and wulfenite

Raman spectra of chillagite, wulfenite, stolzite, scheelite and wolframite were obtained at 298 and 77 K using a Raman microprobe in combination with a thermal stage. Chillagite is a solid solution of wulfenite and stolzite. The spectra of these molybdate minerals are orientation dependent. The band at 695 cm−1 is interpreted as an antisymmetric bridging mode associated with the tungstate chain. The bands at 790 and 881 cm−1 are associated with the antisymmetric and symmetric Ag modes of terminal WO2 whereas the origin of the 806 cm−1 band remains unclear. The ν4(Eg) band was absent for scheelite. The bands at 353 and 401 cm−1 are assigned as either deformation modes or as r(Bg) and δ(Ag) modes of terminal WO2. The band at 462 cm−1 has an equivalent band in the infrared at 455 cm−1 assigned as δas(Au) of the (W2O4)n chain. The band at 508 cm−1 is assigned as νsym(Bg) of the (W2O4)n chain. Copyright © 2002 John Wiley & Sons, Ltd.