To determine the angle of cleavage, look at the intersection of cleavage planes. Commonly, cleavage planes will intersect at 60°, 90° (right angles), or 120°. Be cautious when you see a flat surface on a mineral – not every flat surface is a cleavage plane.

How do you identify cleavage and fracture?

If the crystal splits cleanly and smoothly along a flat plane the break is called cleavage. If the break does not show flat planes, we simply call it fracture.

How is cleavage used to identify rocks?

Cleavage. The way in which a mineral breaks along smooth flat planes is called cleavage. These breaks occur along planes of weakness in the mineral's structure. However, if a mineral breaks along an irregular surface, it does not have cleavage.