Fracture mechanics plays an important role in studies of geologic materials such as rock and coal. Yet, fracture data are scarce for rock and most limited or unreliable for coal. A testing system was developed which can apply mixed mode loads to a crack tip in many rocks and geologic materials. It is possible to subject the test specimen to pure mode I, various mixed modes and a nearly pure mode II fracture load. The system is currently used to study the mechanics of fine fragment formation in various coals. Experimental measurements include K//I and K//I//I, fracture velocity and acoustic emission
