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GMEG presented a collection of Arizona rocks and minerals keyed to a geologic map of the state. Rocks ranged from pieces of recent lava flows, thousand-year-old basalts, to the oldest rocks in the southwest, the Elves Chasm gneiss (1.84 billion years old). They also displayed several fossils, pieces of the base of the North American plate (xenoliths), and a range of other Arizona rocks.