The spectrum for each site was considered as a representative spectrum of the site. Sample of 2 mg is mixed with 40 mg of spectroscopic KBr in the ratio 1:20 using an agate mortar and pestle. Before mixing, necessary amount of KBr powder is dried at 120 C for six hours in an oven. Otherwise the broad spectral peak due to free OH will seriously affect the interpretation on the bound hydroxyls associated with any of the minerals. The major and minor minerals are qualitatively determined by FT-IR technique. The selected samples were analyzed through XRD in Department of Nuclear Physics, Madras University, Chennai, Tamilnadu. The X-ray diffraction powder pattern was recorded at room temperature using Seifert 3003 TT, Germany. X-ray diffractometer having a curved graphite crystal diffracted monochromator, with a source of Cu Ka (k = 1.5420 Å) radiation and NaI (Tl) scintillation counter detector. This software has the capability of least square fitting and other routine refinements and directly outputs the lattice
parameters data. The experimental set-up, its calibration, measurements on standard materials and initial studies using the system were reported by Cullity. The diffraction patterns were obtained over the 2h values in the region of 20–80. The estimated
error in the lattice parameter is of the order of 0.005A. The experimental pattern was compared with patterns obtained from the JCPDS database.