Alliance Resource Partners is a natural resource company. The company is a coal producer in the eastern United States. The company markets its coal production to main domestic and international utilities and industrial users. The company has two reportable segments: Illinois Basin, which comprises of multiple operating segments, including operating mining complexes Webster County Coal's Dotiki mining complex, Gibson County Coal's mining complex, River View's mining complex and the Hamilton mining complex; and Appalachia, which comprises of multiple operating segments, including the Mettiki mining complex, the Tunnel Ridge mining complex, the MC Mining mining complex and the Penn Ridge property.

Contura Energy is a coal supplier with affiliate mining operations across major coal basins in Pennsylvania, Virginia and West Virginia. The company's portfolio of mining operations consists of underground mines, surface mines and coal preparation plants. In the Central Appalachia (CAAP) coal basin, the company mainly produces low-ash metallurgical coal, which are shipped to domestic and international coke and steel producers. In the CAPP coal basin, the company also produces low sulfur, high British thermal unit (BTU) thermal coal for electricity generation, as well as specialty coal for industrial customers. In the Northern Appalachia coal basin, the company produces primarily high-BTU thermal coal.

Cloud Peak Energy is a holding company. Through its subsidiaries, the company is a producer of coal in the U.S. and the Powder River Basin. The company owns and operates three surface coal mines: the Antelope Mine, the Cordero Rojo Mine and the Spring Creek Mine. The company's Antelope Mine and Cordero Rojo Mine are located in Wyoming and its Spring Creek Mine is located in Montana. The company's mines produce subbituminous thermal coal with low sulfur content, and the company sells its coal primarily to domestic and foreign electric utilities. The company has two development projects, the Youngs Creek project and the Big Metal project. As of Dec 31 2017, the company controlled approximately 1,023,900,000 tons of proven and probable reserves.

Hallador Energy is engaged in the production of steam coal from mines located in western Indiana. The company also owns a 50% interest in Sunrise Energy, LLC, a private gas exploration company with operations in Indiana. Additionally, the company owns 100% of Hourglass Sands, LLC, a frac sand mining company in the State of Colorado.

Natural Resource Partners owns, manages and leases a portfolio of mineral properties, including interests in coal, soda ash from trona and other natural resources. The company has two segments: coal royalty and other, which consists primarily of coal royalty properties and coal related transportation and processing assets; and soda ash, which, via Ciner Resources LP, the company's operating partner, mines trona, processes it into soda ash, and distributes the soda ash both domestically and internationally into the glass and chemicals industries. The company's operations are conducted through its NRP (Operating) LLC susbsidiary, and its operating assets are owned by its subsidiaries.