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Iowa State Rock

Geode bridge Mount Pleasant, Iowa.  Photo by Jo Naylor / Flickr (use permitted with attribution).

Official State Rock of Iowa

The geode was designated the official state rock of Iowa in 1967 to promote tourism in the state. Iowa is known worldwide because of the large number of rare and beautiful geodes found in the state. All State Rocks

The area around Keokuk, Iowa is famed for the beauty of the geodes found here. Commonly called "Keokuk geodes," they are sought after by collectors and museums around the world. 

The word "geode" is of Greek origin and means earth-like; geodes are shaped like the earth with a hard outer shell that when cut reveals a core of sparkling mineral crystals (usually quartz and calcite). Southeastern Iowa is one of the state's best geode collecting areas. Geode State Park, in Henry County, is named for the occurrence of geodes. The geode is also the state rock of Oregon (thunderegg).