What is cleavage in relation to minerals?

Cleavage in relation to minerals refers specifically to the tendency of a mineral to break along preferred planes of weakness, resulting in smooth, flat surfaces. This property is a result of the mineral's internal crystal structure, where atomic bonds are weaker in certain directions. As a result, when stress is applied, the mineral will fracture neatly along these planes, showcasing its characteristic cleavage.

This property is important in mineral identification because the angles and shapes of the cleaved surfaces can be distinctive for different minerals. Minerals with good cleavage will show prominent flat surfaces, while those with poor cleavage may not have any distinct planes. The ability to recognize these flat surfaces can help to differentiate minerals that may otherwise appear similar in color or formation.