This study demonstrates the Fourier transform infrared (FTIR) spectroscopic characterization of natural kaolinite from north-eastern India. The compositional and structural studies were carried out at room temperature by using X-ray fluorescence (XRF), electron microprobe (EPMA) analyses and Fourier transform infrared (FTIR) spectroscopic techniques. The main peaks in the infrared spectra reflected Al-OH, Al-O and Si-O functional groups in the high frequency stretching and low frequency bending modes. Few peaks of infrared spectra inferred to the interference peaks for quartz as associated minerals. The present study demonstrates usefulness of the spectroscopic techniques in determining quality and crystalline nature of kaolinite from the Assam and Meghalaya, northeastern India

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We present here optical properties and crystallinity index of quartz (SiO 2 ) in natural rocks samples from the Mikir and Khasi hills, Assam, India. Infrared spectroscopy has been used to study the structure of quartz in rock samples and estimate the mining quality of quartz mineral, which is substantiated by calculating the crystallinity index. Systematic investigations of structure have been carried out in between 10 µm (1000 cm -1 ) and 20 µm (500 cm -1 ) bands of silicates. Investigation is based on the assignment of infrared bands to certain structural groups of SiO 4 tetrahedra. The crystallinity of samples has been ascertained by comparing the ratio of intensity of the characteristic peak at 778 and 695 cm -1 with the corresponding ratio for a standard sample. The crystallinity parameter is calculated by using a standard procedure which can be used to estimate the distribution of quartz in various rocks for mining purpose. The infrared spectroscopic investigation is found to be an ideal tool for structure elucidation and for estimating quartz crystallinity of the natural samples.

A new phase transition in Te from a P-Po-type structure to body-centered-cubic (bcc) structure has been observed at 27+ 3 GPa by using an energy-dispersive x-ray-diffraction technique at high pressures up to 40 GPa. The present structural data are compared~ith earlier data on the superconductivity of Te under high pressure.