Plane or planes along which a stone may likely break or delaminate.
a plane of structural weakness along which a mineral is likely to split
Crystals possess the property of breaking more readily in one or more directions than in others. The planes of easy rupture are called cleavage planes.
A break along crystal planes determined by crystal structure and always parallel to such a plane.
A fracture plane that is preferred.
breakage how a mineral breaks Calcite, Moonstone