Cleavability

Cleavability is a property of a material indicating its tendency to cleave along planes of weakness in its crystal structure when subjected to stress. In mineralogy, cleavability describes how a mineral tends to split along flat, planar surfaces, which are determined by the arrangement of atoms and the presence of weak bonding along specific crystallographic planes.

Cleavage differs from fracture; fracture is irregular breakage, whereas cleavage produces smooth surfaces along distinct crystallographic directions. The quality of cleavability is described using qualitative terms such as perfect, excellent, good, fair, or poor, as well as the number of cleavage directions (one, two, three, etc.).

Factors that influence cleavability include bond strength, crystal lattice anisotropy, planes of weakness, impurities, and moisture. These factors determine the ease and pattern of cleavage and can vary with sample quality and environmental conditions.

Examples commonly cited in mineralogy include mica, which has perfect basal cleavage; halite, with cubic cleavage; gypsum, which cleaves in one or more directions; calcite, with rhombohedral cleavage; and quartz, which tends to fracture conchoidally rather than cleave.

In geology and mining, cleavability influences rock mass behavior during extraction and processing, as well as the design of crushing and grinding operations. In materials science, cleavability affects the machining, polishing, and fracture resistance of crystalline solids. See also cleavage, fracture, and brittleness.