“... Proghorn Thundereggs from the south end of the Mill Creek Wilderness Area in the Ochoco Mountains of Central Oregon are rare. Only a few of this eggs were ever collected, and the location is now closed to collectors. The core (of the presented thunderegg) shows deep red and black water-level agate banding patterns. The shell is wheathered which is typical of these thundereggs...”

From the presentation-programm “These Fabulous Thundereggs”, published by Doug Moore, Stevens Point, 2005