The molecular structure of selected minerals of the rosasite group - An XRD, SEM and infrared spectroscopic study

Minerals in the rosasite mineral group namely rosasite, glaucosphaerite, kolwezite, mcguinnessite have been studied by powder X-ray diffraction, scanning electron microscopy and infrared spectroscopy. X-ray diffraction shows the minerals to be complex mixtures with more than one rosasite mineral observed in each sample. SEM analysis shows the minerals to be fibrous in nature and the use of EDAX enabled the chemical composition of the minerals to be determined. 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 similar to 3401 and 3311 cm(-1). Two intense bands observed at similar to 1096 and 1046 cm(-1) are assigned to v(1) (CO3)(2-) symmetric stretching vibration and the delta OH deformation mode. Multiple bands are found in the 800-900 and 650-750 cm(-1) regions attributed to the v(2) and v(4) bending modes confirming the symmetry reduction of the carbonate anion in the rosasite mineral group as C-2v or C-s. A band at similar to 560 cm-1 is assigned to a CuO stretching mode. (c) 2006 Elsevier Ltd. All rights reserved.