Drift mining
Drift mining is either the mining of a placer deposit by underground methods, or the working of coal seams accessed by adits driven into the surface outcrop of the coal bed. Driftis a more general mining term, meaning a near-horizontal passageway in a mine, following the bed (of coal, for instance) or vein of ore. A drift may or may not intersect the ground surface.This kind of mining is done when the rock or mineral is on the side of a hill.