Alpha Natural Resources will close one of its coal mines in Eastern Kentucky.The company will close the Still House Branch Mine in Cumberland in Eastern Kentucky. Forty miners will lose their jobs, and another 40 will be reassigned to other coal mines. Alpha spokesman Rick Nida says there are several factors that went into the decision to close the mine.“That includes coal-fired power plants closing, competition from low-priced natural gas, high rail rates,” he said. “All of those things combine to make it economically non-competitive.”This is only the latest round in a series of mine layoffs. Alpha slowed production at 10 mines in Kentucky and West Virginia in February, which left more than 150 miners without jobs. The companyclosed several Kentucky mines and slowed production at others in June, laying off 650 workers.Alpha posted anet loss of $2.2 billion in the second quarter of this year, compared with $50 million during the same period last year.