The ancient process of refining gold has already been described under METALLURGY (which see). Most of the Bible references are to the refining of silver (Pr 25:4; Zec 13:9; Isa 48:10). The silver used by the ancients was probably obtained by smelting lead sulfide ore, rich in silver (argentiferous galena). After the ore had been reduced to a metallic condition, the lead was separated from the silver by blowing hot air over the surface of the melted metal. The lead was thus changed to lead oxide which, in a powdered condition, was driven away by the air blast. The resulting lead oxide, called in the Bible silver dross, was used for glazing pottery (Pr 26:23), a use to which it is still put by Syrian potters. The description of refining in Eze 22:18-22 may indicate that a flux (compare "as with lye," Isa 1:25 the [[American Revised Version]] margin) was sometimes added to the melted metal to dissolve the oxides of copper, lead, tin and iron as they formed, thus leaving the silver pure.