placer

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A glacial or alluvial deposit of sand or gravel containing eroded particles of valuable minerals.
• noun A place where a placer deposit is washed to extract its mineral content.

from The Century Dictionary.

• noun In ceramics, a workman in a pottery who places the unburned ware in the saggars and arranges the saggars in the kiln.
• noun In minning, a place where the superficial detritus is washed for gold or other valuable minerals: a word formerly in common use in California, but now nearly obsolete.
• In mining, to mine by the hydraulic process; wash out (gold) from a bank by a stream of water.
• noun One who places, locates, or sets.

from the GNU version of the Collaborative International Dictionary of English.

• noun One who places or sets.
• noun U.S. A deposit of earth, sand, or gravel, containing valuable mineral in particles, especially by the side of a river, or in the bed of a mountain torrent.

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

• noun ethology, Australia, New Zealand A lamb whose mother has died and which has transferred its attachment to an object, such as a bush or rock, in the locality.
• noun mining A deposit of sand or earth in a river-bed etc. which contains particles of gold or other precious minerals.
• noun One who places or arranges something.

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

• noun an alluvial deposit that contains particles of some valuable mineral