My friend, Mr. A. T. Karslake, sent me recently a pareel of crystals from Ceylon, amongst which was a brown tourmaline showing the very rare face z =, (first recorded by Haüy), on whose existence so much doubt has been thrown. The crystal is about ½ inch across, and about ¼ inch in the direction of the axis, and shows well the hemimorphic development. At the analogous pole are r{100} and z, both largely developed, also o {111}, e {110}, s, .