cleavage (mineralogy)

Cleavage is the tendency of a mineral to split along a definite plane parallel to actual or possible crystal faces. For example, galena, whose crystals are cubic, cleaves along three mutually perpendicular planes (parallel to the crystallographic planes 100, 010, 001). Such cleavage is useful in identifying minerals.


Rock cleavage generally takes place between roughly parallel beds whose resistance under deformation to internal shearing differs.