Geodes are fantastical-looking deposits of minerals that crystallize inside a limestone cavity. Although Texas has yielded geodes that are several feet across, most of the geodes found there are about the size of a baseball and have the texture and feel of a dirt clod. Cutting open a geode can take time and effort, but is worth it for the beauty that lies within.
Research areas where geodes are routinely discovered in Texas. Check rock-hunting message boards and look through the Texas State Parks resources. The Palo Duro Canyon, southeast of Amarillo, is the most well-known source of geodes.
Search for geodes in locations where there are exposed limestone formations or in areas that have volcanic ash. You can locate limestone by searching near a known limestone quarry or through the guidance of a park ranger in one of Texas's many state parks. The Edwards Plateau in east-central Texas has huge expanses of limestone. Certain areas of the Quitman Mountains have the right type of volcanic rock to yield geodes.
Check in limestone areas that have signs of visible drainage. Geodes are formed when water drains through a cavity in limestone left by shifting earth, a decomposing animal or washed-out areas. Areas that show erosion and existing drainage can contain geodes.
Gather the rocks that you feel may have geode content and with a chisel and a hammer, tap them gently until they open. If you don't trust yourself to correctly open the geode, take it to an expert that deals in geodes. You can locate an expert by consulting rock-hunting messages boards or taking your raw geodes to a rock and gem show.