Those places are usually still owned by someone. Tracking down claim ownership and getting permission may be pretty hard to do. The GPAA claims in Colorado are good places to start (if you are a GPAA member).
What ever you do, do not collect relics from any these areas - the BLM people can (and will) confiscate your metal detectors and fine you. Looking for gold or silver is fine, but not relics over a certain age. If you hunt on private property (with permission), you can collect relics.
You may want to talk to some people in the various prospecting or metal detecting clubs in Colorado (I am a member of the Colorado Springs GPAA) and find some people to detect with, or get some pointers on where you can look.
Anywhere along a river in the Colorado Mineral Belt, where you see huge piles of rounded rocks (like the stretch between Breckenridge and Fairplay), the river was dredged for gold. Those units dug down to bedrock, but, there was not enough water to wash off the clay and many nuggets encrusted in clay washed right thru the Trommels. These areas are also claimed, but there are places you can get access to (either by paying or knowing people with claims) that are worth your time. There was even a dredge that ran up around Tin Cup (I have not investigated it, altho I have been to that area many times).
There is a lot of fine gold in Colorado (30 mesh and smaller). There is also a lot of Silver Ore that was cast aside when the value of silver dropped in the late 1890's - often you will find it in tailings dumps. Its worth more now than then. It never hurts to know what you are looking for. Your gold detector will work on finding silver Ore. A few pounds of that might make you pretty happy along with any gold you find.
Carry a gold pan to sample with anywhere you go.
The picture I attached shows gold from where a dredge ran near Fairplay (on a Claim I had access to). These were all embedded in clay blobs. The largest is 2.2 grams. Found with a Whites GMT.
