It isn't that difficult to find excellent mineral specimens, some boulder-sized, on National Forest and BLM land in the mountain West. There are many places where people have never been or where a fantastic-looking mineral deposit was ignored because they were too small (common with e.g. copper minerals).

Most of the ones I've found were incidentally discovered while hiking around off-trail in the boonies. I do always bring my Estwing with me just in case though.