ore dressing

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Any treatment of an ore used to concentrate its valuable constituents (minerals) into products (concentrate) of smaller bulk, and simultaneously to collect the worthless material (gangue) into discardable waste (tailings).

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun crushing and separating ore into valuable substances or waste by any of a variety of techniques