Cleavage is the property of a mineral that allows it to break smoothly along specific internal planes (called cleavage planes) when the mineral is struck sharply with a hammer. Fracture is the property of a mineral breaking in a more or less random pattern with no smooth planar surfaces.

How do rock cleavage and mineral cleavage differ?

Breaks along planes of weakness within a rock that are caused by foliation are referred to as rock cleavage, or just cleavage. This is distinct from cleavage in minerals because mineral cleavage happens between atoms within a mineral, but rock cleavage happens between minerals.

What is the difference between a cleavage and a crystal face?

Distinguishing crystal faces from cleavage planes: 1) Crystal faces are normally smooth, whereas cleavage planes, though also smooth, commonly are broken in a step-like fashion; 2) Some crystal faces have fine grooves or ridges on their surfaces, whereas cleavage planes do not.