The average structure of Mg[Al2Si3O10], a stuffed derivative of the high-quartz structure*

Abstract

Similar x-ray diffraction patterns of high quartz and compounds of the chemical composition MgO · Al₂O₃ · xSiO₂ with x = 2–10 show, that these silicates may crystallize in a high-quartz-like structure. A single crystal with x = 3 was used to determine the commonness and differences between high quartz and these high-quartz phases. Only the main reflections of the high-quartz-like subcell have been considered for the investigation, but not additional weak super-structure reflections in form of satellites. Therefore only an average structure could be determined. All atoms take part in the formation of the superstructure by small displacements from the ideal high-quartz positions. The Mg atoms occupy places surrounded by six oxygen atoms.