Discovering Geodes in Idaho

​Geodes​ are round, hollow geological rock formations commonly made of sedimentary or igneous rock. The interiors of geodes are often lined with quartz crystals. Prized by rock hounds and used for decoration and jewelry, geodes are found in many parts of the United States. There are many types of geodes and other rocks in Idaho, which is also known as the Gem State. For those prepared for rock hounding in the state’s scenic, rugged and mineral-rich backcountry, there is a supply of geodes and Idaho thunder eggs available.

Before You Go to Find Geodes

Locate areas in Idaho where geodes are likely to be found. There are several books available on minerals and rocks in Idaho and where they are located. There are also several websites that provide this information, along with lists of gemstones by county.

Acquire detailed maps of the area you wish to search for geodes. Sources of maps include the Bureau of Land Management, United States Forest Service and Idaho Department of Lands. These will help you find your way in and out of an area. The Idaho Geological Survey has maps showing the geological details of an area, which is useful in determining where geodes might be located.

When You Get There

Locate good hunting areas once you reach your destination. Look in volcanic ash beds, and also check gravel deposits and rock formations containing limestone. Geodes congregate in “beds,” and most will be found in the rocky, desert areas of Idaho.

Search the ground for round, lumpy rocks. Distinguish them from other rocks by their shape and by weight. Since they are hollow, see if a round lumpy rock feels lighter than you would expect. Shake it and listen for a rattle made by a loose bit of crystal. Most geodes will be from marble to softball size, although much larger ones are found.

Dig with your shovel or pick. If you are in an area popular with rock hounds, it might be harder to find surface rocks. Also, geodes on the ground indicate more below the surface. Use your pick or rock hammer to loosen potential geodes from rock formations.

Confirming and Cutting Geodes

Confirm geodes by breaking a few open with your rock hammer, looking for hollow interiors and crystal formations. Always wear safety goggles when breaking geodes open, as fragmented pieces of rock can be very dangerous.

Geodes can be cut open at home using a variety of tools, including saws and chisels. However, most of these methods will not produce a clean cut and involve some safety risks. It’s also difficult to cut geodes equally in half, so this task is best saved for a professional with the right tools.

After you have confirmed that some of your rocks are geodes, save most of them to take to a professional for cutting and polishing.