Crystallographers classify twinned crystals by a number of twin laws.

Simple twinned crystals may be contact twins or penetration twins.

There are three modes of formation of twinned crystals.

This is true, for example, also for twinned crystals, ferroelectric domains, and many others.

They were twinned crystals, conjoined and vibrating to inhuman harmonies.

It forms small brown or yellow green crystals, often cruciform twinned crystals.

The typical habit is platy or tabular pseudohexagonal cyclic twinned crystals.

Twinned crystals are not infrequent.

Crystalline material may be divided into single crystals, twin crystals, polycrystals, and crystal powder.

Thus, snowflakes form euhedral, six-sided twinned crystals.

Gypsum occurs in nature as flattened and often twinned crystals, and transparent, cleavable masses called selenite.

An example of mineral-to-mineral substitution is replacement of aragonite twin crystals by native copper, as occurs at Corococo, Bolivia.

Georges Friedel also synthesised Calcium aluminate (1903) in the framework of his work on the Macles theory (twin crystals).

Twin crystals, on the other hand, consist of single-crystalline twin domains, which are aligned by twin laws and separated by domain walls.

Tsumebite occurs at Morenci, Arizona, predominantly as twinned crystals associated with wulfenite, olivenite and the hyalite variety of opal.

These twinned crystals have a hexagonal appearance, but are the result of a triplet of twins with each "twin" oriented at 120 to its neighbors and taking up 120 of the cyclic trilling.

Crystals can be marred by twinning, which can occur when a unit cell can pack equally favorably in multiple orientations; although recent advances in computational methods may allow solving the structure of some twinned crystals.