Chapter 1.3 Twinning

Mathematical, physical and chemical tables

First Online Edition (2006)

Part 1. Crystal geometry and symmetry

  1. E. Koch

Published Online: 1 JAN 2006

DOI: 10.1107/97809553602060000574

International Tables for Crystallography

International Tables for Crystallography

How to Cite

Koch, E. 2006. Twinning. International Tables for Crystallography. C:1:1.3:10–14.

Author Information

  1. Institut für Mineralogie, Petrologie und Kristallographie, Universität Marburg, Hans-Meerwein-Strasse, D-35032 Marburg, Germany

Publication History

  1. Published Online: 1 JAN 2006


In Section 1.3.1, general terms with reference to twinning are explained. Subsequently, the terms ‘twin lattice’ and ‘twin index’ are defined and illustrated by several examples in Section 1.3.2 and the implication of twinning on the reflection pattern in reciprocal space is discussed in Section 1.3.3. Twinning by merohedry and by pseudo-merohedry is described in Section 1.3.4. For each combination of point group and Bravais lattice, the possible twin operations for twins by merohedry are given in Table Table shows the simulated Laue classes, the extinction symbols, the simulated ‘possible space groups’ and the possible true space groups for crystals twinned by merohedry. For cases in which the twin element cannot be recognized by direct inspection, a procedure for the calculation of the twin element is described in Section 1.3.5.


  • calculation of the twin element;
  • lattices;
  • twins;
  • twinning