Marble and monzogranite specimens were subjected to displacement-controlled diametral compression tests for the characterization of the cracking pattern according to AE parameters, three-dimensional localization of the AE sources and petrographic analysis. The tests included unload-reload cycles after peak. Microcracking in monzogranite and marble was initiated at approximately 90% and 60% of the peak load, respectively. Before peak load, both rocks showed the development of microcracks uniformly distributed on the plane containing the loading edges. At the post-peak stage, new micro cracks were first concentrated on one of the faces at the center of the specimen along the loading axis and then spread through its thickness all the way to the other face. The main portion of the micro cracking in marble was concentrated just after peak, while in monzogranite it extended through to the end of the test. The microcracking process in monzogranite was initiated and propagated mainly through quartz crystals, not along visible weakness planes and it released high-level energy, while in marble it followed the cleavage planes and released low-level energy. (C) 2016 Elsevier Ltd. All rights reserved.