klyvingsflater

Klyvingsflater, or cleavage planes, are flat surfaces along which a mineral or rock tends to split when subjected to stress. They arise from the crystal structure and the distribution of bonds within minerals, creating planes of weakness that allow relatively easy detachment. Cleavage is distinct from fracture, which is a non-planar break that does not follow crystallographic planes.

In minerals, klyvingsflater can occur in one, two, or three or more directions. A mineral with one good cleavage is said to have a single cleavage direction; two directions intersect at characteristic angles; three directions form a set of planes that meet to give a roughly rhombohedral or cubic geometry, depending on the crystal system. Common examples include muscovite, which has a very regular basal cleavage along the {001} plane; calcite, which shows rhombohedral cleavage in three directions; halite, which has three perpendicular cleavage planes; and fluorite, which exhibits four cleavage directions in an octahedral arrangement.

Cleavage planes are influenced by metamorphic and sedimentary history as well as mineralogical composition. In metamorphic rocks, macroscopic cleavage such as slaty cleavage or schistosity results from the alignment of platy minerals during deformation, producing surfaces along which the rock readily splits.

Observation and application: cleavage is assessed by preparing or breaking samples to reveal smooth, flat surfaces that indicate the directions and quality of cleavage. Knowledge of klyvingsflater aids mineral identification, rock classification, and practical activities such as mining, quarrying, and construction, where the ease of splitting affects handling and stability. Cleavage strength varies with temperature, pressure, and chemical composition.