"Made of mercury but coated in gold". Translators did a goof there huh? Mercury? Cheap jewelry is probably made of tin or zinc, or possibly copper, brass or bronze. Alternatively, aluminum, but since the local merchants didn't had their eyes bug out of their heads because they were holding fortunes beyond their wildest dreams (aluminum pre-modern days was absurdly expensive, it'd like making a solid gold bracelet and coating it in copper) I think we can eliminate that possibility.