The Green Copper Mine is a copper mine site outside of Goodsprings, Nevada. I wasn’t able to visit this site because it is now used as a private shooting range. I walked for about an hour and a half with the dog only to find a monster truck advertising machine guns at the entry way to the mine.
You can actually drive directly to the gate for this mine. Since it’s private and used for a live firing range of machine guns, I wouldn’t recommend trespassing.