Geode Field!

Rabbit Springs Geode Field, also known as Rabbit Springs Thundereggs, is a well-known rockhounding site located in southern Idaho near the Nevada border. It’s a popular spot for collectors seeking thundereggs—spherical rocks that often contain beautiful agate or crystal-filled centers, some of which fluoresce under UV light due to mineral content like chalcedony or quartz. This site sits along U.S. Highway 93, roughly 38 miles from Twin Falls, Idaho, and about 130 miles from Mountain Home, making it accessible yet remote enough to feel like a true adventure.
The coordinates for Rabbit Springs are approximately 42.06572°N, -114.67387°W. You can get there by driving south from Twin Falls toward Jackpot, Nevada, and looking for the old Rabbit Springs rest area, a historical marker for the site. The terrain is rugged, typical of the high desert landscape in this region, with volcanic and sedimentary rocks from ancient geological activity providing the perfect conditions for thunderegg formation. These rocks are remnants of gas pockets in lava flows that filled with silica-rich fluids over millions of years.
No heavy digging is necessary here—surface collecting with a bucket is the way to go, as many thundereggs are weathered out and scattered across the ground. A rock hammer might come in handy to crack them open, but locals and seasoned rockhounds suggest the best finds are often already exposed, and breaking into the bedrock isn’t worth the effort. The thundereggs vary in size, from plums to grapefruits, and some glow a striking green or orange under a 365nm UV light, thanks to trace minerals. Rumors of radioactivity have floated around, but tests with Geiger counters have debunked that myth.
The site is on public land managed by the Bureau of Land Management (BLM), so casual collecting is allowed as long as you’re not using heavy machinery or digging extensive tunnels—stick to hand tools and surface finds. Any vehicle can make the trip, though the final approach might involve a short walk from the highway. September’s cooler weather makes it an ideal time to visit, avoiding the summer heat of this arid region.