Vibrational spectroscopy of selected minerals of the rosasite group

Abstract

Minerals in the rosasite group namely rosasite, glaucosphaerite, kolwezite, mcguinnessite have been studied by a combination of infrared and Raman spectroscopy. The spectral patterns for the minerals rosasite, glaucosphaerite, kolwezite and mcguinnessite are similar to that of malachite implying the molecular structure is similar to malachite. A comparison is made with the spectrum of malachite. The rosasite mineral group is characterised by two OH stretching vibrations at ~3401 and 3311 cm-1. Two intense bands observed at ~ 1096 and 1046 cm-1 are assigned to ν1 (CO3)2- symmetric stretching vibration and the δ OH deformation mode. Multiple bands are found in the 800 to 900 cm-1 and 650 to 750 cm-1 regions attributed to the ν2 and ν4 bending modes confirming the symmetry reduction of the carbonate anion in the rosasite mineral group as C2v or Cs. A band at ~560 cm-1 is assigned to a CuO stretching mode.