In the first nine months of 2015, Stockton produced 151,523 clean tons of coal, up 28.1% over the 118,279 tons it turned out in the same period of 2014, the company said in late October. Run-of-mine output was even higher — 365,985 tons in the first three quarters of this year, or a 30.3% rise over 243,527 tons in the year-ago period.

According to the company, total coal sales were 186,186 tons for the nine months ended September 30, compared with 112,831 tons for the first three quarters of 2014, a 65% gain.

Stockton had 26,149 clean tons of coal in inventory at the end of September, versus only 8,839 tons a year earlier.

Steve Best, Atlantic’s managing director, said he was pleased with Stockton’s performance, especially “when viewed against the very challenging market conditions for commodities, in particular for thermal and metallurgical coals, the prices of which have plunged dramatically.”

In contrast, he said, anthracite prices “have held up well and we will be raising the prices of all our anthracite grades by $10 a ton” in October “to take advantage of the healthy market for anthracite as we move into what is traditionally our best period of the year for both sales volumes and prices.”

He was referring to the traditional home and industrial heating season in Pennsylvania and other areas of the northeastern U.S. where more anthracite coal is burned in the winter months.

For the first time since Stockton opened several years ago, “we have a very healthy inventory of clean coal which means that we have the confidence to supply our traditional customer base and also to go out and seek new customers,” Best said.

With the steel industry experiencing global reductions in production in terms of anthracite use, “this is being counterbalanced by an increase in demand for anthracite to replace high-sulfur petroleum coke with a consequent increase in demand from that sector which also bodes well for the future as the steel industry recovers,” he added.

Best said Stockton’s improvement is being driven by Atlantic’s investment in new plant and equipment that has boosted capacity and reliability. “Our Komatsu PC3000 hydraulic excavator gives us 98% availability and the combination of mining the almost solid Mammoth seam and improvements to the washing plant have resulted in an almost 37% increase in our wash recovery rate,” he added.

Mining at Stockton is close to reaching the bottom of the coal basin in the current cut, he said, and “according to indications from old underground mine maps, we are due to enter the almost solid 30-ft-thick Mammoth seam, which will further assist in maintaining our high production levels.”

All anthracite coal in the U.S. is mined in several counties in northeastern Pennsylvania. Since the latter half of 2014, the state’s anthracite producers have experienced renewed interest from prospective European customers because of the continuing conflict in the Ukraine.