Study of Structural Disorder in Natural Tourmalines by Infrared Spectroscopy

Fourier Transformation Infrared (FTIR) spectroscopy in the range 2000-10000 cm^-1 was used to examine tourmalines from metarhyolites near Majjur within the Gadag Schist Belt and are compared with those from known compositions from quartz vein from gold mineralised area. FTIR spectra in this region are comprised of fundamental and combinational vibrational modes of hydroxyl ions delineating their structural environment. In these samples three fundamental vibrations observed at 3730-3720, 3637-3627 and 3550-3500 cm^-1 and combination modes at 4529, 4454, 4356 and 4238 cm^-1, and the Electron Probe analysis indicate that the tourmalines could be classified in to dravite-schrol series. However, additional shoulder mode observed around 3490 cm^-1 in tourmaline from Gadag Schist Belt, indicates structural disorder.