North Eastern region of India has a substantial deposit of high sulfur Tertiary coals, ranging from Paleocene to Oligocene period. These coals are of recent origin and have different physico-chemical attributes in comparison to other Indian coals. The general characteristics, which restrict their usage in the domestic as well as industrial sectors, are high sulfur, high volatile matter, low ash fusion temperature, highly caking and friable nature. This book describes the incorporation of sulfur in Tertiary Indian coals under the influence of marine sulfate sources. The book contains five chapters which cover the formation of coal, the mechanism of sulfur incorporation in coals, geology, and sulfur functionalities in NE Indian coals. The coverage also extends to possible sources of sulfur under marine environment, relationship of sulfur with other constituents of coals, formation of pyritic and organic sulfur in coals. Thus, an attempt has been made to provide a comprehensive coverage of all the major processes involved in sulfur incorporation in these coals. The book is expected to be of relevance to all the researchers of the area.