Certain twin laws are more common in particular crystal systems, and they are also diagnostic features for many minerals. Repeated, or multiple, twins are three or more twins repeated by the same twin law. If the twin law defines a rotation axis, then cyclic twinning results. Cyclic twinning of aragonite, which has an orthorhombic structure, can result in formation of crystals with a nearly perfect 6-fold rotation axis. Growth twinning results from the emplacement of atoms on the outside of a growing crystal in such a way that the regular arrangement of the lattice is interrupted.
Transformation twinning occurs in pre-existing crystals and thus is a secondary form of twinning.