gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1972.038.300.13 Short Communications On the Blue Colour of Natural Banded Fluorites Calas Georges Laboratorie de Minéralogie-Cristallographie Université de Paris VI 12 1972 38 300 977 979 13 3 1972 Copyright © 1972, The Mineralogical Society 1972