gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1977.041.320.07 An Intergrowth of Calcic Labradorite in a Plagioclase-Quartz-Biotite Gneiss from Broken Hill, New South Wales Phillips Evan R. Chenhall Bryan E. Stone Ian J. Pemberton J. W. Department of Geology, University of Wollongong, Wollongong, N.S.W. 2500, Australia 12 1977 41 320 469 471 29 11 1976 4 1 1977 Copyright © 1977, The Mineralogical Society 1977 Summary

Compositions of An61 and An69·5 have been determined for two domains in plagioclase from a gneiss. Optical properties indicate that the same compositions apply respectively for an intergrowth of ‘matrix’ and lamellae found in zones between the domains. The intergrowth appears to span the composition range between the Bøggild and Huttenlocher intergrowths.