A mining technique often used by surface mine operations when the overburden becomes too thick for the coal to be mined economically using traditional surface mining methods. Large-diameter (usually 2-4 feet) horizontal holes are drilled as much as 300 feet into the v vertical face of the coal bed by an auger. Like a bit used for boring holes in wood, coal augers consist of a cutting head with a screw-like extension. As the auger turns, the head breaks up the coal and the screw carried it back into a conveyor that loads it directly into a truck.