Columbia subject headings:
Gold--Metallurgy.
Mercury--Metallurgy.
Metallurgy.
Mineral industries--United States.
Silver--Metallurgy.
Harvard subject headings:
Gold--Metallurgy
Mercury--Metallurgy.
Metallurgy.
Mineral industries--United States
Silver--Metallurgy
Princeton subject headings:
Gold--Metallurgy.
Mercury--Metallurgy.
Metallurgy.
Mineral industries--United States.
Silver--Metallurgy.