Coal: Vitrinite Reflectance and Maturity
The process of organic matter transformation in sedimentary basins with increasing temperature is called maturation. With respect to petroleum generation, organic matter may be immature, mature or overmature. The reactions involved are irreversible. In order to describe the maturation process, different maturation parameters have been established among which vitrinite reflectance is (one of) the most commonly used. Other maturation parameters used for coals include (organic) carbon content, yield of volatile matter, moisture content and calorific value.
Using incident light microscopy, three types of organic particles (i.e. maceral groups) are generally recognized: inertinite, vitrinite, and liptinite. Vitrinite is derived from parts of higher land plants which are primarily rich in cellulose or lignin, e.g. wood. Vitrinite reflectance was first used to measure accurately and rapidly the rank of coals. The observation that vitrinite particles