When in Montana the one stone to find is Montana Agate. Apparently once prolific in and along the Yellowstone river now very rare indeed. I cheated I purchased thing slices from a couple different rock shops in Montana. Some of it is very scenic and other more patterns, another of nature's little amazements which is hidden in the disguise of just a old grey rock, unassuming until you break it open and slice it thinly then we see the full magic.
The odds and ends in the creative world of Thendara M Kida-Gee.