Coal resource classification system of the U.S. Geological Survey

In order to use coal resource terms with precision and common understanding and to compare resource data effectively, the authors developed a standardized, definitive, broadly applicable classification system to derive uniform, coordinated coal resource estimates. The principles of the system for all mineral resources ape given in USGS Circular 831. Personnel engaged in coal resources work are to use the definitions, criteria, guidelines, and instructions incorporated in this coal resource classification system in all U.S.