# Twin law

### From Online Dictionary of Crystallography

Loi de macle (Fr). Legge di geminazione (It)

# Twin law

The twin law expresses the operation that generate a twin. It is indicated by the symbol of the twinning element of symmetry: $\bar 1$, [uvw] and (hkl) for the centre of symmetry (inversion twin, direction of the rotation axis rotation twinand Miller indices of the mirror plane reflection twin, in the order. Usually, instead of the single (hkl) plane, the symbol {hkl} is used to indicate all the planes equivalent for symmetry.

Chapter 3.3 of International Tables of Crystallography, Volume D