Pyroelectrically caused twisting of quartz crystals

The twisting of quartz crystals is conditioned by Dauphine twinning. Each twisted crystal shows morphological characteristics confirming this type of quartz twinning. A linear mathematical correlation based on morphological parameters measured on quartz crystals elongated and twisted along their polar [EQUATION] a-axis has been deduced. It was demonstrated that the twisting angle is the function of the twisting constant and some of the crystal dimensions. This constant has the same value ~4° as the declination of the [EQUATION] edge of the crystal twisted around the [EQUATION] a-axis which also corresponds to the surface distribution of the positive charge observed with Dauphine-twinned quartz crystal on cooling. A similar quartz feature is the twisting of a quartz crystal around the c-axis. A proposed theory describing the reasons for crystal twisting, development of different crystal forms and types of twisted quartz crystals is thus based on the pyroelectrically accelerated growth from slowly cooling and slightly supersaturated quartz-bearing solutions.