Influence of quartz crystal origin on ferrobielastic twinning observed by X-ray topography

In this paper, we report the ferrobielastic twinning in AT-cut samples issued from natural (Brazil and Madagascar) and synthetic (from Sawyer company) quartz crystals. The experiments have been carried out using an uniaxial stressing equipment for which the stress is applied in a suitable direction of the quartz sample. The stress level associated with the optical appearance of the twinned domains and coercive stress values are presented for each material. It has been observed that these stress levels are smaller for synthetic quartz than for natural one. The observations of the twin wall propagation were made by X-ray topographs obtained with synchrotron radiations. Transmission Laue patterns due to the white X-ray beam were taken at several compressive stress levels. As visualisation of a twin domain is governed by contrasts generated in topographs of chosen lattice planes, we notice that the twinned domain does not disappear after putting off the pressure. Additionally, the content of lattice impurities such as Al, Li, Na, K and broad OH band are given.