Can Fracture Toughness be Used as a Proxi for Fracability?

From a fracture mechanical point of view, the fracture propagation in rock material and hence how easily rock can fracture is described by fracture toughness. Fracture toughness is a parameter that describes the resistance of the rock to the propagation of a fracture. In the theory of fracture mechanics, the stress intensity factor K is a measure of the amount of stress concentration at the tip of a crack as a function of applied load and fracture length. The fracture toughness KC is the critical value of the stress intensity factor at which an existing fracture extends. From this mathematical framework it derives that longer fractures are in general easier to propagate.