The Collaborative International Dictionary of English v.0.48:

mined \mined\ adj.
   extracted from a source of supply as of minerals from the
   earth. [Narrower terms: deep-mined; exploited;
   strip-mined]
   [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

deep-mined \deep-mined\ adj.
   taken from an undergrround mine; -- as contrasted with coal
   obtained from a strip mine; as, deep-mined coal.
   [WordNet 1.5]

WordNet (r) 3.0 (2006):

deep-mined
    adj 1: of coal, as contrasted with coal obtained from a strip
           mine; "deep-mined coal"