Through the use of nondestructive testing techniques, the Bureau of Mines is pursuing a goal of improving the efficiency of the rock excavation process. Toward this end, 44 laboratory tests were conducted to identify a practical method of monitoring fracture development in rock, as caused by an excavation tool. An acoustic emission (ae) transducer was used to monitor the test samples as they were loaded. The signal from this instrument was recorded in real time along with the radial and axial loads generated by the fracturing device. Through the review of these signals on a common- time base, it was possible to see the relationship between the developing fracture and the loading conditions. As a part of the posttesting investigations, samples that were incompletely fractured were sawn and ground to expose the fractures. Visual examination of these samples allowed approximations to be made of the total surface created. Surface area approximations were also made for the completely fractured samples. Quantitative analyses of the ae signals were conducted for comparisons with the calculated surface areas.