Coal quality were gathered from various sources and put in a geologic framework. The economic Jewel Seam forms part of the Lower Cretaceous Gates Formation and has a stratigraphic thickness of 10 m. Its depositional setting was on a coastal plain, well removed from marine clastic influences. Shortening of the strata by folding and thrusting amounted to 50 percent, often resulting in structural thickening of the Jewel Seam.
Ash and sulfur are largely determined by the original sedimentary environment. Volatile matter, fixed carbon, carbon, hydrogen and vitrinite reflectance are determined by subsequent burial and to some extent by deformation. Vertical sequences with upward increase in ash and low ash zones through the center of the Jewel Seam can be explained by the original chemical environment of the swamp. Average finely disseminated ash is about 14 percent. In places the disseminated ash content has increased by tectonic shearing. For mining purposes, the 2 m sampling interval of the Jewel Seam results in a good characterization of ash variation. Sulfur contents of the Jewel Seam are low compared to those of many other coal deposits and average 0.3 percent. Sulfur, which is mostly organic, often shows elevated values at the base, and to some extent at the top of the seam. Volatile matter, fixed carbon, carbon, hydrogen and vitrinite reflectance are largely determined by depth and length of burial to some extent by deformation.
Rank of the Jewel Seam ranges from high to medium volatile bituminous, where the highest rank is found in the central part of the study area. The intersections of isorank surfaces and the Jewel Seam indicate components of syndeformational coalification. A good linear correlation between maximum vitrinite reflectance and volatile matter (dry and ash free) is observed. A contoured map of vitrinite reflectance predicts rank and volatile matter of the Jewel Seam for unexplored parts of the coalfield.