Hobbies And Interests
Facts
"Geode" was derived from the Greek word "geoides," meaning "earth-like" and indicates a rock with a hollow cavity lined with crystals, such as quartz, amethyst, or calcite.
Formation
A geode begins as a bubble in volcanic rock or a hollow in sedimentary rock. The outer shell of the bubble or hollow will eventually harden, and water forms on the inside of the cavity. The water contains silica precipitation that contains a variety of dissolved minerals.
Structure
The silica will cool in layers, resulting in crystals of different minerals inside the cavity of the geode. This process occurs over thousands of years.
Geography
Geodes can be found all over the world, but the largest concentrations occur in deserts. Volcanic ash beds are also common geode locations.
Fun Fact
Keokuk, Iowa, has one of the best known geode sites in the United States. According to the Iowa Department of Natural Resources, Keokuk is one of the most productive and famous collecting regions in the world. Iowa adopted the geode as the state rock in 1967 in honor of Keokuk's fame.