Coal Petrology - A Shifting Role from Coal Utilization to Fuel Exploration

Coal petrology deals with the study of microscopically recognizable remains of vegetal source matter, termed 'macerals', which for convenience are classified and categorized into three main groups- vitrinite (O2-rich), liptinite (H2-rich) and inertinite (C-rich). Each maceral being specific in its origin, evolution and environmental conditions during genesis has tremendous interpretative value. Vitrinite-rich coals form in anaerobic (wet-reducing) condition, whereas aerobic (dry-oxidative) condition results into the formation of inertinite-rich coals. Macerals of the liptinite group originate in acidic-wet conditions of swamp. Optical properties (reflectance and fluorescence) and quantitative estimations of coal micro-constituents overall reflect the chemical properties and thus help in various interpretations. The studies are convincingly utilized to predict the suitability of coal for specific economic and industrial purposes. Currently, the petrological investigations are being utilized to interpret the potentiality of coal for methane that originates during the time and pressure induced diagenetic and catagenetic stages of coal formation.