Abstract: Rock has heterogeneity and discontinuity and rock's dynamic fracture property has been one of the hotspots and challenges in domestic and foreign studies.The paper studies the applicability of caustics to rock type media, hoping to have a general view of the caustics speckles surrounding the crack tip.The results show that no caustic speckles is found in three types of rock materials.The causes for being hard to shoot or even finding no caustics speckles in rock type materials are pointed out from viewpoints of experiment and theoretical estimation.

Key words: Rock, Dynamic fracture, Caustics method