By Margaret Mills, Updated Mar 24, 2022
Geodes are spherical, hollow rock formations that often contain quartz crystals lining their interiors. They are prized by collectors for their beauty and are commonly used in jewelry and home décor. Idaho, known as the Gem State, offers a wealth of geodes, as well as the famed thunder eggs that sometimes appear in the same mineral‑rich regions.
Plan ahead by researching locations where geodes are most likely to occur. A variety of reference books and online databases provide detailed information on Idaho’s mineral deposits, including county‑specific listings. Consult resources such as the Idaho Geological Survey, the Bureau of Land Management, the United States Forest Service, and the Idaho Department of Lands for both topographic and geological maps that highlight potential geode beds.
Prepare the necessary gear: sturdy hiking boots, a reliable GPS or compass, a rock hammer or pick, a shovel, safety goggles, a waterproof bag or bucket, water, sunscreen, and a map of the area. These items will help you navigate the rugged backcountry safely and efficiently.
Geodes tend to cluster in specific sedimentary or volcanic settings, such as ash beds, gravel deposits, and limestone outcrops. Search for rounded, lumpy rocks that feel noticeably lighter than their solid counterparts; a hollow interior often produces a faint rattle when shaken. Typical geodes range from marble‑size to softball size, though larger specimens can occasionally be found.
Use a shovel or pick to excavate surface rocks. In popular rock‑hounding areas, surface geodes may be scarce, but their presence often indicates additional specimens lying beneath the ground. Gently loosen surrounding material with a rock hammer to free potential geodes without damaging them.
To confirm a geode, break a small section with a rock hammer while wearing safety goggles to protect against shards. A true geode will reveal a hollow cavity lined with crystal formations. Although it is possible to cut a geode at home with saws or chisels, the process is typically messy and risky. For a clean, polished result, it is best to send confirmed geodes to a professional cutter who can expertly split and polish the interior.
Quartz‑lined geodes are most commonly found in the upper valley of Lost River (Custer County), near the DeLamar Silver Mine (Owyhee County), and northwest of Weiser (Washington County). Collecting on Idaho public lands generally does not require permits, but always verify restrictions and obtain permission when accessing private property.
Adhere to the “Rockhound’s Code of Ethics,” which emphasizes respecting private property, closing gates, and leaving no trace of your visit. A copy of the code is available on the Idaho Department of Lands Gemstone Guides webpage.
