Cleavage refers to the propensity of crystalline minerals, such as diamond, to split in one or more directions either along or parallel to certain planes, when struck by a blow. These planes of relative weakness are a result of the regular locations of the crystal’s atoms. This creates smooth repeating surfaces in the crystal. Cleavage is one of the two methods used by diamond cutters to split rough diamond crystals in preparation for the cutting process (sawing is the other method).