Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

K. N. Prakash Narasimha ¹, Krishnaveni ¹, P. S. R. Prasad ², H. Ramalingaiah ¹, J. S. Venu Gopal ³

Affiliations
1 Department of Geology, University of Mysore, Mysore - 570 006, IN
2 M P D, N G R I, Hyderabad-500 007, IN
3 Center for Neo-Ecofriendly Studies and Training, Mysore, IN

Abstract

Vermiculite mineralization in the Gopalpura area, Karnataka in the Archean supracrustal rocks of the Sargur Group occurs as discontinuous lenses and pockets within the ultramafic rock and at the contact with acid intrusives. Detailed mineralogy as studied using microscopy, X-Ray diffraction, infrared spectroscopy, differential thermal analyses, and electron microprobe analyses are presented. The probable origin of the vermiculite from biotite through hydrobiotite is discussed.

Keywords

Vermiculite, Sargurs, Gopalpura, Mysore District, Karnataka.

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P. S. R. Prasad ¹, T. N. Gowd ¹

Affiliations
1 Mineral Physics Division, National Geophysical Research Institute, Hyderabad - 500 007, IN

Abstract

Fourier transform infrared (FTIR) spectroscopic investigations on naturally occurring topaz sample were carried out in 400 - 5000 cm^-1 wave number range, using recently established facility in NGRI, to identify the nature of hydroxyl ions. Three bands were observed around 1162, 3646 and 4795 cm^-1, which were due to hydroxyl ions. A strong asymmetry in both (OH) stretching and combination modes, observed for the first time, confirm the non equivalence of the proton sites in its crystal structure. Electron paramagnetic resonance (EPR) studies showed two resonance lines with 'g' values of 2.01 and 1.967, confirming existence of naturally occurring crystallographic defects.

Keywords

Topaz, FTIR, EPR, Hydroxyl Ions

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