Rabbit Springs is located 5 miles north of the Nevada border in Southern Idaho, a short distance off Highway 93. This area is a well-known destination for rockhounding enthusiasts seeking distinctive fluorescent thundereggs (an uncommon rock type in Idaho). This site is notable not only for its easy access but also for the abundance of small, hollow thundereggs scattered across the surface of the lava flow.

This site includes the old highway and a road cut from the newer highway. A volcanic bed of thunderegg-bearing rhyolite has been exposed during construction, and over time, weathering and erosion continue to bring more material to the surface

Despite being close to the highway, the area is remote, characterized by a high desert landscape of dry and open terrain, rolling hills, flat sagebrush plains, and scattered rocky outcrops of volcanic origin.

Fluorescent Thunderegg Rockhounding at Rabbit Springs

Rabbit Springs is famous for its abundance of thundereggs that fluoresce under a long-wave ultraviolet blacklight at 365 nm. Bring a portable UV light to spot the greenish—and occasionally pink—fluorescence inside the rocks.

The thundereggs are typically round to slightly lumpy, ranging from 2 to 5 inches in diameter. Larger specimens can be found with digging, but most surface finds are smaller and weathered. They have a light to dark brown, sometimes reddish matrix, and often contain:

Chalcedony - Bluish-gray showing a greenish glow under UV light
Agate - Typically gray, white, or bluish, sometimes banded
Quartz crystals - Occasionally forming in small pockets or cavities.

You’ll find thundereggs just lying on the ground, waiting to be picked up. While most surface specimens are small or broken, with a bit of digging, you can uncover larger, intact thundereggs — sometimes up to 6 inches across.

Best part? No special tools are required for surface collecting—just your eyes and a bit of patience. If you are looking for larger specimens, bring a geological pick and try shallow digging.

Note. Experienced collectors occasionally report low-level radioactivity in rhyolite-hosted specimens, including thundereggs. Since Rabbit Springs thundereggs originate from volcanic rhyolite, they may contain trace amounts of naturally occurring radioactive elements. However, I used my Gamma-Scout Geiger Counter and did not detect any elevated radiation levels in the specimens I tested. Always follow safety rules when collecting minerals.

Dangerous Rocks & Minerals: How to Stay Safe While Rockhounding

Beyond Rabbit Springs Rockhounding

It’s a good idea to explore other nearby sites while visiting Rabbit Springs. The old highway road provides additional access to BLM land, and blue-gray agate and chalcedony have been reported in the area south of Rabbit Springs. The region around Salmon Falls Creek Reservoir is also known for its potential to yield thundereggs.

Since Rabbit Springs is in a remote area, it’s a great idea to find a relaxing spot after a long day of rockhounding. Nat-Soo-Pah Hot Springs Resort, located just 25 miles north of the thunderegg collecting site, offers a refreshing soak in mineral-rich water. In addition to its hot spring pools, the resort offers several amenities and a campground featuring tent sites and full RV hookups.

Free dispersed camping is permitted on BLM land surrounding the Rabbit Springs collection sites. There are no services available, so please bring your water and pack out all your trash. The peace, quiet, and star-filled sky make it a perfect spot for rockhounds who like simple camping.

If you prefer more comfortable accommodations, lodging is available in Twin Falls, approximately an hour north, and even closer in Jackpot, Nevada—just about 6 miles south.

Lodging in Twin Falls, Idaho

Lodging in Jackpot, Nevada