Answer:
Copper
Step-by-step explanation:
In 2017, USA is fourth largest producer of copper in the whole world. The first three are Chile, China and Peru. Copper mining has been a major industry in USA since 1840s. In 2017 it produced 1.27 million metric tonne copper. Aluminum is another element produced in USA. In 2014, it was sixth largest Aluminum producer in the world.
Mercury has not been produced in USA since 1992. Although USA is a big consumer of diamonds, very few diamonds are produced here.