A deposit carrying several economic metals at once, most often some combination of zinc, lead, copper, silver and gold.
A mineral deposit containing economically significant quantities of two or more metals, such as copper-gold, zinc-lead-silver, or cobalt-nickel. Polymetallic deposits offer revenue diversification but require more complex metallurgy and processing.
By-product credits can make or break a polymetallic project, and they introduce exposure to metals the company may never mention in its marketing. They are also why equivalence grades exist, and why those grades need reading carefully.