Historically, December has been a particularly tragic month in U.S. coal mining.
Considered the worst mining accident ever, explosions at West Virginia’s Monongah Nos. 6 and 8 in 1906 claimed 362 lives. Twenty-seven miners perished in an underground fire caused by a faulty air compressor at the Wilberg Mine in Utah in 1984. And a blast that rocked the South Mountain No. 3 mine in Virginia in 1992 killed eight miners, leading investigators to discover that improper ventilation, examinations and rock dusting contributed to the deadly accident.