The presence of pyrite in coal has often been attributed to being a factor in spontaneous combustion, but quantifying the effect has been problematical from a hazard assessment viewpoint. A simplistic approach of correlating high sulphur content with the presence of reactive pyrite is unreliable and can be misleading. Pyrite needs to be present in an appropriate form (size and morphology) to enhance its oxidation potential. Consequently, it is important to be able to identify and quantify any reactive pyrite contribution to coal mine heatings in a systematic and scientific manner. In 1992, the US Bureau of Mines recognised there was a deficiency in existing testing techniques and recommended that these would need to be changed to assess the effect of pyrite in the self-heating process. Recent advances in adiabatic oven testing have led to development of a new spontaneous combustion Incubation Test that is used to benchmark coal self-heating against the known performance of case history coals. This test is capable of measuring the pyrite oxidation reaction for site-specific conditions and not only quantifies the minimum incubation period for pyrite initiated events to develop, but also shows the manner in which they develop.