In the Illinois Basin, coal-bearing rocks of Pennsylvanian age underlie 36,800 mi² in Illinois, 6,500 mi² in southwestern Indiana, and 6,400 mi² in western Kentucky. From 1890 to 1998, about 10.2 billion short tons (bst) of coal were produced from all coals in the basin. Coal production in 2000 was about 88.4 million short tons. The major producing coals are the Springfield, Herrin, Danville, and Baker Coals. This assessment provides overviews of the geologic setting, distribution, quantity, and quality of these coals. The main products are: 1) updated coal resource estimates categorized by state, mining district, county, geologic reliability of the estimate, and coal thickness and depth, 2) regional and statewide maps that depict coal extent, thickness, elevation (structure), mined-out areas, areas where the coal may potentially be mined at the surface or underground, and geographic distributions of ash, sulfur, and major, minor, and trace-element contents, and 3) digital databases that contain all publicly available point-source data on thickness, depth, and coal quality. This assessment was a cooperative effort between the State Geological Surveys of Illinois, Indiana, and Kentucky and the U.S. Geological Survey.

Assessment results include:

Danville and Baker Coals – Remaining, identified resources in deposits >42 in. thick and at depths <150 ft are estimated at 1.4 bst; for depths >150 ft, 9.2 bst. Mean ash yield is 11.9 % (n=334), sulfur content, 2.9 % (n=335), mercury content, 0.11 ppm (n=39), and arsenic content, 19 ppm (n=39). Mean, as-received, calorific value is 10,920 Btu/lb (n=295).

Herrin Coal – Remaining, identified resources in deposits >42 in. thick and at depths <150 ft are estimated at 6.3 bst; for depths >150 ft, 62.4 bst. Mean ash yield is 10.8 % (n=2,542), sulfur content, 3.0 % (n=2,517), mercury content, 0.12 ppm (n=206), and arsenic content, 6 ppm (n=216). Mean, as-received, calorific value is 11,170 Btu/lb (n=2,390)., and

Springfield Coal – Remaining, identified resources in deposits >42 in. thick and at depths <150 ft are estimated at 5.7 bst; for depths >150 ft, 60.0 bst. Mean ash yield is 11.2 % (n=1,832), sulfur content, 3.5 % (n=1,830), mercury content, 0.12 ppm (n=123), and arsenic content, 12 ppm (n=145). Mean, as-received, calorific value is 11,280 Btu/lb (n=1,770).