Twin and topotactic growth of β-eucryptite dendrites and their lattice coincidence analysed by the reticular theory

The crystallographic orientation of β-eucryptite dendrites has been analysed by the electron backscatter diffraction technique, and a twin relationship and a topotactic relationship between dendrites have been found. The twin index n = 2 and the obliquity ω = 3.2877°.

Electron backscatter diffraction study of twins and intergrowths among quartz crystals in granite

It is shown that the Dauphiné twin is very abundant but the other twin laws (Japan, Esterel, Sardinian, Breithaupt and Cornish) are very rare for the quartz in the granite of Tiantangzhai pluton (China). Besides twin laws, many intergrowths based on overlapping faces are found, and these faces are simply the twin planes of the Japan, Esterel, Sardinian, Breithaupt and Cornish twin laws.