Many distinct types of fracture surface markings are found in a wide variety of materials. Those found in rocks can be classified as hackle and rib markings and further sub-divided according to geometrical structure. The geometry, occurrence, micro- and macrostructure of hackle markings are examined in detail. It is found that hackle markings consist of a series of microfractures whose orientations vary according to zonal relationships and that their geometry is controlled by the properties of the interfaces (e.g., bedding). A mechanism of stress wave induced microfracturing is proposed as the cause of fracture surface markings. The properties of stress waves which are used to develop the theory are summarised. The zones of interaction of incident and reflected stresses resulting from a non-instantaneous pulse source adjacent to one or more interfaces are examined, and methods for resolving the stresses within these zones are developed. Principal stress trajectories are constructed for different source and interface conditions. By altering one or more of the variables, the principal stress trajectories predict microfracturing orientated according to the different geometries of all types of surface markings. The properties of the interfaces are established as the dominant control of hackle mark morphology. The influence of stress waves on the propagation of brittle fractures is demonstrated, and it is predicted that hackle markings are, in general, diagnostic of shear macrofracture.