INTRODUCTION The tri-state area of southeast Iowa, northeast Missouri and western Illinois, is renowned for its geodes. Geodes from the Keokuk area contain a variety of minerals, but quartz is dominant in most. Beautiful transparent to white quartz crystals cover the interior walls of many geodes. Chalcedony forms the outer shell in all Keokuk geodes. White, gray, blue, yellow or orange chalcedony also encrust the interior walls of many geodes. Calcite is common and occurs in many crystal habits and colors. An additional 17 minerals have been identified in Keokuk geodes; some of the more noteworthy include: kaolinite, dolomite, pyrite and sphalerite. The following is a list, including contact information, for the major commercial collecting locations in the Keokuk area. You should call each of the following locations before you go for details. Jacob's Geode Shop and Mine 823 East County Rd 1220 Hamilton, IL 62341 (217) 847-3509 Dennis Stevenson Geodes Nick's Geodes Sheffler's Rock Shop and Geode Minee Check out Roctoberfest 2007 for McRocks.com reports about the Geode Fest 2007. If a more natural look is preferred, you have two available options for opening them. First, the geode should be placed onto the ground and a score line should be made around the entire circumference with a hammer and flat chisel. You may have to go around and around the circumference of the geode several times to create get a good score. After the scoring, slightly more force should be applied to the score mark with the hammer and chisel until a crack develops. The crack can then be opened up by prying with a screwdriver so you can end up with two near equal halves. The second and much easier and effective method for opening geodes would be a wheeler-type soil pipe cutter.
 Wheeler-Rex 590 Soil Pipe Cutter Wheels integrated into the chain apply even pressure around the entire circumference of the geode and split it into equal halves. A pipe cutter is generally considered the best way of opening Keokuk area geodes since it is much easier than scoring and whacking with hammer and chisel and the helps protect delicate crystals. However, a soil pipe cutter like the one pictured above will only crack geodes up to around 10-inches in diameter. Larger pipe cutters are available but are very costly so that scoring and whacking method is, by default, the preferred method to crack very large geodes. The following pictures illustrate the proper use of a soil pipe cutter.
 CLEANING DIRT & IRON OXIDE STAINING A power washer is the best way to remove dirt and other debris from inside and outside of a geode. However, you should be careful about how much pressure you apply (use a fine spray) when a geode contains delicate minerals. Some geodes that contain extremely delicate minerals, such as millerite, that will not hold up to water at any pressure should not be cleaned at all but left as is. Wear sturdy gloves and safety glasses if you have to hold the geode to spray it.To remove the iron oxide from quartz and other minerals that will hold up to being cleaned by water, Iron Out rust stain remover may be employed according to the following procedure:
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"Keokuk Geodes", having been named after the city of Keokuk, Iowa located in the heart of the collecting area. Most of the geodes are derived from the lower Warsaw Formation, a widespread rock unit of Mississippian age. Calcium carbonate and clay muds deposited in a shallow sea about 340 million years ago were subsequently lithified to form the shales, shaley dolomites, and limestones. Geodes can be dug out of exposures of the 
lower Warsaw Formation where they are concentrated in certain layers. Loose geodes can also be collected in stream channels where water has eroded the rock. 
and cracking of minerals such as large quartz crystals is a concern, you should find a way to heat up the specimens slowly such as in the kitchen sink using a water sprayer. You should start with a warm spray and gradually (over about 3 to 5 minutes) turn up the heat to maximum and then you can submerge the specimens in very hot water.