Sudden and dynamic failure of rock/coal mass during mining is a serious threat to safety in underground mines. This failure is often referred to as ‘rockbursts’ or ‘coal bursts’, mainly attributable to high level of stress. In order to investigate the coal burst phenomenon, a series of laboratory tests were conducted to examine the failure patterns associated with a burst event. Optical glass cube samples were drilled under varying stress conditions, to investigate the influence of stress environment on the dynamic failure. The outcomes of these laboratory tests will improve the understanding of the loading mechanisms leading to coal burst, especially the influence of high stress environment.