
Drift mining is either the mining of an ore deposit by underground methods, or the working of coal seams accessed by adits driven into the surface outcrop of the coal bed. Drift is 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 t...
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http://en.wikipedia.org/wiki/Drift_mining

tunneling into the side of a hill where mineral deposits are in horizontal layers; a rough topography prevents surface mining
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http://www.encyclo.co.uk/visitor-contributions.php
No exact match found.