Hydromtellurgy is a subset of Metallurgy, and is used to process Gold and Silver.

rolled gold

Thomas Kirke Rose has written:

'The metallurgy of gold' -- subject(s): Gold, Metallurgy, Assaying

They aren't because they had gold metallurgy.

Gold plating is slightly different from rolled gold. Gold plating is depositing a thin layer of gold onto the surface of another metal like copper or silver by chemical or electrochemical plating. Rolled gold is the same as gold filled where a solid gold layer of gold is bonded with heat and pressure to a metal like brass. So although very similar, the difference is in how the gold is being held to the initial metal.