The best places to look for geodes are in the desert, in volcanic ash beds or in places with high concentrations of limestone. In the United States, that includes parts of California, Arizona, Utah and Nevada. Iowa is also a good spot to search, and the geode is their state rock. Geodes are round rocks that have a hollow cavity that is lined with crystals. The color and type of crystals are only revealed when the rock is opened.
Some collectors prefer to collect a bucket of geodes and then crack them in the field. One method is to score the circumference of the geode using a hammer and a chisel, then hitting the score mark with more force until it cracks. A screwdriver placed in the crack usually pops it into two halves. If the geode is filled with solid rock, usually agate, it's called a nodule. Some of the most prized geodes are filled with purple amethyst crystals.
The cracking method allows the display of the geodes or nodules in their natural state. Cutting them in half with a rock saw allows the ends to be polished using a flat lapidary machine. This works much like a record player, constantly spinning while coarse and then fine grinding materials smooth the edges.
Hunting for geodes usually involves traveling to remote areas. Emergency food and water should be carried and vehicles, preferably four-wheel-drives, should be in top shape. Traveling in small groups with at least two vehicles is best. Remote areas may also bring geode hunters face to face with cougars or other wild animals, another good reason to travel in groups. .