Summary:
HCC extracts coal from the Herrin (Illinois No. 6) coal seam located in the Illinois Basin. The Illinois Basin is an interior cratonic basin that formed from numerous subsidence and uplift events. The Illinois Basin extends approximately 80, 000 square miles, covering Illinois, southern Indiana, and western Kentucky.
Primary coal-bearing strata, including the Herrin and Springfield (Illinois No 5) seams, are in formations of Pennsylvanian aged rocks, which were deposited about 325 to 290 million years ago. The Pennsylvanian System is characterized by many vertical changes in lithology. There are over five hundred distinct beds of shale, sandstone, sandy shale, limestone, and coal in the Pennsylvanian System in Illinois. Many beds are laterally extensive and can be correlated across much of the Illinois Basin because of their position in relation to distinct marker beds, such as coals and limestones.
Pennsylvanian rocks in Hamilton County consist of shale, sandstone, siltstone, coal, and limestone. Pennsylvanian rocks are classified in Illinois in three groups, the McCormick, the Kewanee, and the McLeansboro. The Kewanee Group contains the most abundant reserves of coal. Within the Kewanee Group is the Carbondale formation. The Herrin and Springfield belong to this formation.
Local Geology
Herrin Seam:
The immediate roof over a vast majority of the reserve is a black, fissile shale known as the Anna Shale. The Anna Shale is generally between one to two feet thick but can thicken to eight feet in some areas. The Anna Shale is overlain by a dark gray, fine grained, argillaceous limestone known as the Brereton Limestone. This limestone is commonly four to five feet thick. In some locations, this limestone is absent. This limestone member is critical in providing roof stability at Hamilton. The Energy Shale, a silty gray shale associated with over bank deposits of the Walshville paleochannel, can form the immediate roof in localized areas. The Energy Shale occurs in lenses and can cause roof instability, requiring additional support.
Springfield Seam:
The silty, gray Dykersburg Shale, ranges from zero to about four feet thick, and forms the immediate roof of the Springfield seam. When the Dykersburg Shale is absent, it is replaced by the black, brittle, Turner Mine Shale, which ranges from about one to three feet thick in the HCC resource area. The thin, argillaceous St. David Limestone lies above the Turner Mine Shale, ranging from zero to about three feet in thickness. The gray, silty Canton Shale separates the St. David Limestone from the Briar Hill (5a) coal seam and Vermillionville Sandstone. The Vermillionville Sandstone occurs in two distinct units which are separated by a shale or sandy shale zone. This water bearing sandstone can encroach on the immediate and main roof of the Springfield seam. In these areas, ground control issues associated with water and differential compaction can occur requiring additional support to maintain roof stability.
Property Geology and Mineralization
Hamilton extracts coal from the Herrin seam. The seam lies between about 600 and 1100 feet deep across the resource/reserve area and dips gently to the east/southeast. The seam varies in thickness from about 5 feet to 9 feet. On a 1.60 float, dry basis, the Herrin seam averages approximately 8.2% ash, 2.8% sulfur, and 13,375 btu/lb. The Herrin seam mineral deposit type (coal rank) is a high volatile bituminous B/C coal.
The Springfield seam underlies the Herrin seam by approximately 100 feet. This seam is extensively mined throughout the Illinois basin. On a 1.60 float, dry basis, the Springfield seam averages approximately 8.4% ash, 2.5% sulfur, and 13,400 btu/lb. The Springfield seam mineral deposit type (coal rank) is a high volatile bituminous B/C coal.
The primary coal-bearing strata is of Carboniferous age in the Pennsylvanian system.
The geologic model developed to characterize the resource/reserve is a bedded sedimentary deposit model. This is generally described as a continuous, non-complex, typical cyclothem sequence that follows a bedded sedimentary sequence. The geology, including coal thickness and extent has been and continues to be verified by an extensive drilling program.