Alpha-quartz 1. Crystallography and crystal defects

Crystallography of alpha-quartz is discussed with special reference to the existing ambiguities regarding handedness of its enantiomorphic forms and a mnemonic has been suggested. Previous x-ray diffraction topographic studies of synthetic quartz are critically reviewed and analysed to understand the origin, nature and location of dislocations. It is suggested that dislocations associated with cell boundaries, characteristic of the Z-zone grown portions of synthetic quartz, are pure a-type edge dislocations but possibly with an alternating non-conservative climb component associated with the predominating glide component.