Synthese und Kristallstruktur des Eukryptits, LiAlSiO₄

Crystals of the mineral eucryptite, LiAlSiO₄, have been prepared synthetically as hexagonal bipyramids up to 5 mm. long, having weak negative birefringence and strong optical activity. The space group is C6₂2 (or its enantiomorph C6₄2) and the cell dimensions are a = 5.27 A., c = 11.25 A. The atomic co-ordinates have been determined and show the structure to be closely related to that of high quartz. The Al and Si ions occupy the sites of the Si ions in quartz, and the small Li ions are accommodated in the channels in the structure.