In the log book of some of the caches you will find a number for part of the co-ords for the final Bonus cache up in the mine area.
The Golden Cross Mine is open to the public in the day time and the gated near the start of the mine area are locked at night.
Bring the family and go for a walk around the mine area and find a few other caches at the same time.
Mind out for cars on the road when you stop to find the cache.