This document defines the principle and the methods for the determination of the fragmentability coefficient of rocky material. The fragmentability coefficient IFR distinguishes the behaviour of certain rocky material and is used to show the change in particle size from the moment than the material is excavated through to its subsequent implementation and in certain cases during its whole service life. Changes in the particle size occur due to the structural resistance of the rock being unable to support the mechanical stress to which it is subjected during its implementation and use.