The company acquired the final coal reserves for $40m and closed the deal.
Once the full production of longwall begins at the Deer Run, the annual production of coal is estimated to be 7 to 9 million tons.
Natural Resource Partners President and chief operating officer Nick Carter said, "The Deer Run mine will be one of the lowest cost underground coal mines in the country with access to four different railroads and the river markets which bodes well for the marketing of this coal in any type of market conditions."
The company reported earning revenue of $2.9m in the first half of 2012 based of the production of approximately 630,000 tons related to the development of the mine.
Natural Resource financed the acquisition with its credit facility.
US-based Natural Resource Partners owns and manages mineral reserve properties.
