The Copperopolis Mine in Yavapai County, Arizona was started in 1884 and the settlement of the same name instituted a post office the same year. Edward Hasting was the postmaster.
The only remains of Copperopolis are the walls of a cabin there, and the grave of Annie Mae White, who died June 8, 1939. There are reputed to be as many as a dozen unmarked graves.
Like the name implies, the Copperopolis mine was primarily a copper mine, with some aluminum and iron being present. No mention of gold or other precious metals are mentioned in assay reports. Apparently the mine was not very successful. Many other mines are nearby in these Bradshaw Mountains--and in this case, getting there was at least half the fun.
If you wish to locate the mine and surroundings the following coordinates will get you there on GoogleEarth: N 34.0794, W 112.4636.
I have never seen anything unusual in a mine before, but at the 21:36:26 time on the video you will see something unexplainable fly (very quickly) from left to right on the screen. It is worth noting that I had the only light source in the mine, which was pitch dark except for a faint light from the vertical shaft twenty or thirty feet ahead. What was it? I have NO idea.
Anyone who has seen the video on the 'Exploring Abandoned Mines & Unusual Places' video of the Horton Mine knows that sometimes strange things are seen & heard in old mines.