35 Mile Radius Surrounding Keokuk, Iowa
Iowa named the geode their state rock in 1967. The prime hunting location for geodes is in a 35-mile radius of Keokuk, Iowa, and they range in size from 2 to 6 inches in diameter, although some as large as 30 inches have been found. About twenty different minerals have been found in the Keokuk geodes with quartz being the most common. Calcite and pyrite are also found and often there are attractive combinations of several minerals. The geodes are found in certain layers of the Mississippian age Warsaw Formation, where they weather out of the host shaley dolomite and limestone.
Southeastern Iowa is the home of Geode State Park, named for these unusual specimens..
Keokuk Geodes

Shefflers Geode Mine   CLOSED

Lowell, Iowa – Muddy Creek
Location: Search the entire creek if possible, may need permission in some areas.
Geodes

Warsaw, Illinois - Geode Glen Park
Location: Route 136 through Hamilton, IL. to Great River Road. 5 miles to Warsaw, Ill.

Bedford, Indiana
Location: Geodes with a  variety of minerals can be found in limestone outcroppings along Hwy. 37 about 10 miles north of Bedford  just south of the Monroe Lake exit.
Geodes containing Barite, Calcite, Dolomite, Marcasite, Millerite, Pyrite, Quartz, and Sphalerite

Bloomington, Indiana
Location: South of Bloomington to a large roadcut at the Harrodsburg Exit.
Geodes

Harrodsburg Indiana
Location:  No definite site

Washington Count around Salem Indiana
Location:  No definite site

Dannville Kentucky
Location:  No definite site