gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1969.037.287.12 Study of Minerals from the Pegmatites of the Nellore Mica-Belt, Andhra Pradesh, India Part III—Biotite Babu V. R. R. M. Department of Geology, Andhra University, Waltair 9 1969 37 287 391 393 8 11 1968 Copyright © 1969, The Mineralogical Society 1969 Summary

The biotites in the pegmatites are Fe2+ type. X-ray analyses indicated that they are 1M or 3T polymorphs. In the colour of the biotite iron plays an important role. From the Fe/(Fe+Mg) ratios, the analysed biotites are assumed to have crystallized between 760 and 500 °C.