sweepwasher

from The Century Dictionary.

• noun In gold- and silver-refining, a person who extracts from the sweepings, potsherds, etc., the small particles of gold or silver contained in them.

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

• noun One who extracts the residuum of precious metals from the sweepings, potsherds, etc., of refineries of gold and silver, or places where these metals are used.

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

• noun dated One who extracts the residuum of precious metals from the sweepings, potsherds, etc., of refineries of gold and silver, or places where those metals are used.