Infrared and infrared emission spectroscopy of the zinc carbonate mineral smithsonite

Infrared emission and infrared spectroscopy has been used to study a series of selected natural smithsonites from different origins. An intense broad infrared band at 1440 cm−1 is assigned to the ν3ν3 CO32− antisymmetric stretching vibration. An additional band is resolved at 1335 cm−1. An intense sharp Raman band at 1092 cm−1 is assigned to the CO32− symmetric stretching vibration. Infrared emission spectra show a broad antisymmetric band at 1442 cm−1 shifting to lower wavenumbers with thermal treatment. A band observed at 870 cm−1 with a band of lesser intensity at 842 cm−1 shifts to higher wavenumbers upon thermal treatment and is observed at 865 cm−1 at 400 °C and is assigned to the CO32−ν2ν2 mode. No ν2ν2 bending modes are observed in the Raman spectra for smithsonite. The band at 746 cm−1 shifts to 743 cm−1 at 400 °C and is attributed to the CO32−ν4ν4 in phase bending modes. Two infrared bands at 744 and around 729 cm−1 are assigned to the ν4ν4 in phase bending mode. Multiple bands may be attributed to the structural distortion ZnO6 octahedron. This structural distortion is brought about by the substitution of Zn by some other cation. A number of bands at 2499, 2597, 2858, 2954 and 2991 cm−1 in both the IE and infrared spectra are attributed to combination bands.