Located in Chile, El Teniente is the world's largest underground mine for what metal?

I never thought copper was all that valuable until a big run of thefts of copper wiring in my city.

SneakyMole92698, regarding how valuable copper is we have this suggestion. Go to your local library and look at some children's books I'm in. You just might be astounded where and in how many places and in Buried wage will find Copper being used.