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 A(g) modes of terminal WO2 whereas the origin of the 806 cm(-1) band remains unclear. The nu(4)(E-g) band was absent for scheelite. The bands at 353 and 401 cm(-1) are assigned as either deformation modes or as r(B-g) and delta(A(g)) modes of terminal WO2. The band at 462cm(-1) has an equivalent band in the infrared at 455 cm(-1) assigned as delta(as)(A(u)) of the (W2O4)(n) chain. The band at 508 cm(-1) is assigned as nu(sym)(B-g) of the (W2O4)(n) chain. Copyright (C) 2002 John Wiley Sons, Ltd.