Investigators told AAP that the victim, Robert Smith, was in a cart when the vehicle veered off an underground path and overturned.
The Pattiki room-and-pillar mine produced 2.4 million tonnes in 2012.
A longwall miner at Consol Energy’s McElroy mine in northern West Virginia died the previous day.
Reports suggest that Roger King, 62, received fatal head injuries when a conveyor chain broke during a longwall panel move.
The two fatalities have taken the US coal death toll to 16 this calendar year.