Montana is the Treasure State, so of course rock hounding is a popular pastime. Montana's history is based on the discovery of gold, gems, and other minerals - today there are so many resources and groups for those who love rocks, gems, and geology.
Tourists are paying big bucks for the "cowboy" experience. Three of the best dude ranches in the US are in Montana and guests aren't blinking at the price.
Cool rocks and gemstones have been my jam since I was a little kid. Every family road trip would have me scouring the roadsides for "Rock Shop" signs or anything of the like.