Company officials said notices have been issued to 60 employees under the Work Adjustment and Retraining Notification Act. Furloughs will occur over 14 days starting December 1.

The affected workers were officially briefed on the situation in an October 1 meeting. All employees will have the option to take a position at another Consol mine.

The company said Mine 84 had higher mining costs than current market prices, even though spot prices have been improving in the region.

"Mine 84 has been in operation for many decades, and it is unfortunate that the time has come when it was no longer able to compete in today's markets," Consol operations senior vice-president Jimmy Brock said.

The Pennsylvania producer initially announced that it would close Mine 84 in 2007, and laid off about 500 workers in 2008.

According to company data, Mine 84 – which produces from the prolific Pittsburgh 8 seam in southwestern Pennsylvania via longwall and room-and-pillar methods – had 3.6 million tons of output in 2007.

Federal data reflects it as a nonproducing operation, with 1.83Mt output in 2008, just over 514,000t in 2009 and no output in 2010.