gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1980.043.331.14 Changes in the Crystal Morphology of Synthetic Reedmergnerite (NaBSi3O8) During Ordering Experiments Mason R. A. Dept. of Geology, The University, Manchester M13 9PL, Great Britain*

Present address: The University of Chicago, Dept. of the Geophysical Sciences, 5734 S. Ellis Avenue, Chicago, Illinois 60637, USA.

 9 1980 43 331 905 908 15 1 1980 Copyright © 1980, The Mineralogical Society 1980 Summary

The morphologies of hydrothermally grown reedmergnerite crystals change systematically with time and rate of change of B, Si order. Three stages in this process are recognized: (1) Growth of well-faceted crystals. (2) Development of etching leading to the formation of irregular grains. (3) Modification of irregular grains to form rounded or ellipsoidal crystals. A solutionreprecipitation process is responsible for the morphological changes and the increase in degree of order of B and Si with time at constant temperature and pressure.