There is nothing wrong with treasure hunting, recreational mining and the like. Just be aware that it is hard work, and sometimes there can be dangers. There are some important laws regarding mining on public lands that people need to be aware of also. Rock hounding for things like jasper, chert, flint, turquiose, garnet, etc is a lot of fun and can be practiced all over the country. Metal detectors are great for getting out and finding historical artifacts and lost valuables. Just be aware of the laws and respect private property.
Looking at old mines and ghost towns is a way of life in places like Nevada. It is fun to explore the old towns and camps. Goldfield, NV is my favorite example. It has about 100 residents now but in 1904 the president came by train for the big prize fight to a town of about 35,00 people.