ABSTRACT
The mechanism of cleavage The cleavage property of a gemstone is of particular interest to the lapidary and the diamond cutter. Like other properties possessed by minerals, cleavage is a directional feature and can only exist in crystalline substances. Cleavage occurs in a gemstone as a well-defined plane of weak atomic bonding, which allows the stone to be split in two leaving reasonably flat surfaces. These cleavage planes are always parallel to a crystal face in a perfectly formed single crystal. In some gemstones which have cleavage properties, however, the crystal faces may not always be present as a convenient guide to the direction of the cleavage plane. Furthermore, if the stone happens to be microcrystalline or polycrystalline this will inhibit any cleavage property which might otherwise have been present in a single-crystal specimen of the mineral.
