It is a major milestone in the development of the overall mining complex, with the mine designed to produce more than 3 million short tons of coal on an annualised basis.

The majority of the output will be sold into domestic and international metallurgical coal markets for use in the production of steel.

The Leer mine is poised to become a world-class supplier of metallurgical coal and a cornerstone of Arch's Appalachian operations for many years to come, Arch CEO John Eaves said.

“We applaud the great work of the Leer team in completing this significant step and we look forward to a safe, productive and profitable future for this important new mine,” he said.

Arch has invested more than $400 million to develop the Leer mine, which produces a high-quality, high-volatile "A" coking coal product that is attracting significant interest in world metallurgical markets.

Eaves said with its 400-person workforce and highly efficient longwall system, the mine would benefit from a very competitive cost structure once it scaled up to full production.

“Our investment in the Leer mine underscores our commitment to West Virginia and our focus on producing the highest quality metallurgical coals to meet the needs of global steelmakers,” he said.

“With the addition of Leer, we are advancing our long-term strategic objective of increasing our penetration into domestic and seaborne coking coal markets,” he said.

Arch operates six metallurgical and pulverised coal injection-grade mines in Appalachia, including four in West Virginia.

Arch also has significant undeveloped metallurgical coal reserves in the region.