Bruneau Jasper Thundereggs are some of most popular jaspers and they're widely used in lapidary arts. They're best known for their "orbs/eggs" features that are sometimes revealed when cutting the brown to orange jasper-filled thundereggs. There had been reports of difficult mining to extract the jaspers out of the rhyolite lava beds/welded ash beds and the claims are still maintained today in spite of the words about the area being turned into a national wilderness.  The actual problem may be that the roads up the canyon being so eroded that it's becoming quite dangerous to drive there. That issue may will stay there until some one decides to improve the accessiblity by repairing the roads or adding an alternate road to the boat ramps.
    It started with the mud filling in the cavities within the thundereggs and water would start to act on the mud, coloring it or producing the "orbs/eggs" within them. The colors are typically brown to orange with some yellow features, and some specimens come with red, black, brown, and green colors. Some jaspers did suffer some cracking as a result of drying before the cracks were filled and welded by silica solutions, giving them "morrsonite" look.