hy·dro·met·al·lur·gy 
(hī′drō-mĕtl-ûr′jē)
(hī′drō-mĕtl-ûr′jē)n.
The treatment of metal or the separation of metal from ores and ore concentrates by liquid processes, such as leaching, extraction, and precipitation.
hy′dro·met′al·lurgi·cal adj.