December 18, 2025 - Today, Core Natural Resources, Inc. (NYSE: CNR) ("Core," the "company," "we" or "our") announced that it has resumed longwall operations at its Leer South metallurgical mine in Barbour County, West Virginia. The longwall system had been idle since January 13, 2025, when combustion-related activity was detected in a previously mined area.

In addition, Core announced that its West Elk longwall mine in Colorado is now executing at consistent productivity levels following a period of transition associated with its move to the B-Seam, and Core expects that improved performance to continue in future periods.

"On behalf of the entire board and management team, I commend the operations team for making safety their highest priority in the successful recovery, repositioning, and restart of the longwall system," said Jimmy Brock, Core's chairman and chief executive officer. "In addition, we want to again extend our appreciation to federal, state and local regulatory officials for their collaboration and support. Leer South is a highly strategic asset, and we fully expect this world-class operation to execute at a high level in 2026 and beyond. While the issues at Leer South and West Elk adversely affected Core's performance in 2025, we are looking forward to strong cost improvement and profitability at both these operations going forward."

The Core team was successful in recovering the major mining equipment at Leer South, including the 209 hydraulic shields, face conveyor, shearer, stage loader, crusher, and power system. The equipment was generally in good condition, with limited damage despite the prolonged period of inactivity. Following the repositioning of the longwall system, the operations team permanently sealed the affected area of the Leer South mine, effectively eliminating any potential future issues associated with this combustion event.

"The Core operations team has displayed tremendous professionalism, dedication, and – most importantly – the highest commitment to safety throughout this process at Leer South," said George Schuller Jr., Core's senior vice president and chief operating officer. "We expect Leer South to enter 2026 fully ramped and operating efficiently, with an exceptionally strong outlook for operational excellence going forward."

In aggregate, Core expects a significant step-up in its financial performance in 2026 due to the restart at Leer South; the much improved geological conditions at West Elk; substantial insurance recoveries stemming principally from the combustion event at Leer South; the cessation of the fire-suppression and idling costs at Leer South; and the full-year benefit of substantial and ongoing merger-related synergies.

About Core Natural Resources, Inc.

Core Natural Resources, Inc. (NYSE: CNR) is a world-class producer of high-quality metallurgical and high calorific value thermal coals for the global marketplace. Core's highly skilled workforce operates a best-in-sector portfolio of large-scale, low-cost longwall mines, including the Pennsylvania Mining Complex, Leer, Leer South, and West Elk mines, along with one of the world's largest and most productive surface mines, Black Thunder. The company plays an essential role in meeting the world's growing need for steel, infrastructure, and energy, while simultaneously serving the resurgent requirements of the U.S. power generation fleet. Core has an extensive and strategic logistical network – anchored by ownership positions in two East Coast marine export terminals – that provides reliable and efficient access to seaborne coal markets. The company's deeply ingrained culture is grounded in safety and compliance, continuous improvement, and financial performance, with an emphasis on stakeholder engagement and stockholder returns. Core was created in January 2025 via the merger of long-time industry leaders CONSOL Energy and Arch Resources and is based in Canonsburg, Pennsylvania.