Raman spectra of minerals containing interconnected As(Sb)O3 pyramids: trippkeite and schafarzikite

Oriented single-crystals of trippkeite (CuAs 2 O 4 ) and an isostructural mineral schafarzikite (FeSb 2 O 4 ) were investigated by polarized Raman spectroscopy. The internal vibrations, i.e. the stretching and bending modes, of trippkeite occur between 250 and 850 cm -1 , and those of schafarzikite between 200 and 750 cm -1 . The higher mass and the longer bond distances of the SbO 3 groups readily explain the lower wavenumbers of the latter. Comparing the spectra of minerals containing XO 3 pyramids with those of the minerals from the present study, approximate similarities in the spectral features are evident. A clear distinction between Raman spectra of separated and interconnected (As,Sb)O 3 groups is not observed.