A few areas in the United States are well-known for their geodes and geode-like objects. Geodes are so popular in a few states that they have achieved the status of “official state rock” or “official state gem.” The Iowa State General Assembly designated the “quartz geode” as the official “state rock” in 1967. The Oregon Senate designated the Thunderegg as the official “state rock” in 1965. And, the Minnesota Legislature designated the Lake Superior agate as the official state gem in 1969. Some of the more noteworthy localities are described below. There are many more, and a good place to read about some of them is in a book titled Geodes: Nature’s Treasures by Brad L. Cross and June Culp Zeitner.