See the parking waypoint for the suggested route description.
There is a date at the entrance to the mine scratched into the rock that says "1917". A gate was placed at the mine entrance about 10 years ago. The mine goes back about 150 yards. I strongly recommend you bring a strong flashlight so you can look into the mine.
After signing the cache, If you go NW from the cache, and search in the rocks by the stream you can find garnets.
The Colorado School of Mines Geology Museum (free, and open to the public) has a sample from this mine, Specimen 15:15 which is copper and malachite. It was donated by Captain Berthoud. Captain Berthoud's grave is in the Golden Cemetery. Berthoud Pass was named after him. He helped establish the Colorado School of Mines in 1870. He was the first professor of geology at the school.
Additional Waypoints
PK5WNQG - GC5WNQG Parking
N 39° 44.397 W 105° 13.888
You can park at the end of Bonvue, and then go through the gap in the fence. Follow the faint trail until you see the tire on the fence post, then head uphill to the post. Eventually you will come across another faint trail that leads to the mine.