Jointing is the deformation mechanism responsible for joints. Jointing may happen under a variety of remotely applied tensile, compressive stresses, or internal fluid pressure when the magnitude of local tensile stress at a point, usually a flaw tip, exceeds some measure of the rock's tensile strength or fracture toughness. Each stage of jointing is discussed under initiation, propagation, and termination dealing with individual isolated joints and with interaction between neighboring joints.