The New Mexico Bureau of Mines and Mineral Resources (NMBM&MR), with the participation of other individuals, has been involved in a long-term coal quality study. This project was funded by the New Mexico Research and Development Institute (NMRDI) with contributions from several companies. The NMBM&MR has developed a large data set for the San Juan basin coal fields using quality data from this project and data collected from public and private sources through an 11-yr cooperative project with the U.S. Geological Survey (USGS) for entry into the National Coal Resource Data System (NCRDS). The most complete set of quality and thickness data exists for the economically important Fruitland Formation coals.

Evaluation of these data suggest that some trends in the attributes of the Fruitland coals exist. The trends appear to support the premise that the characteristics of these coals are a consequence of their depositional environments. These environments were influenced by the relative position of the shoreline and the rate of shoreline movement. The thickness and quantity of the coals and the ash and sulfur content appear to be significantly influenced by their position relative to the shoreline and the rate of shoreline shift. The moisture content and Btu value appear to have been influenced by these same controls, but the degree of coalification of the northern Fruitland Formation coals has also been influenced by the heat from the massive intrusive complexes of the La Plata and San Juan Mountains in southern Colorado.