Oregon Thunderegg Ref: 0174
Oregon Thunderegg Ref: 0174
Oregon designated the thunderegg as its official state rock in 1965. Geologically known as lithophysae, thundereggs are spherical, nodule-like stones found in rhyolitic volcanic ash and lava flows. While they look rough and nondescript on the outside, cutting and polishing them reveals intricate interiors filled with agate, jasper, and opal.
🏛️ History & Legend
According to Central Oregon folklore, the name "thunderegg" originates from a legend of the Warm Springs Native Americans. The local tribes supposedly believed the nodules were missiles thrown by angry "Thunder Spirits" or gods living on Mount Jefferson and Mount Hood during violent thunderstorms.
🗺️ Where They Are Found
Oregon is widely considered one of the best places in the world to find thundereggs. The largest deposits are concentrated in the high desert of Central and Eastern Oregon, primarily in the following counties:
- Crook
- Jefferson
- Malheur
- Wasco
- Wheeler
Famous digging sites include Pony Butte, the Priday Agate Beds (historically located near Madras), and areas near Succor Creek.
🔬 Mineralogical Properties
| Property | Specification |
|---|---|
| Geological Name | Lithophysae |
| Host Rock | Rhyolitic volcanic ash & lava flows |
| Interior Fill | Agate, jasper, and/or opal |
| Exterior | Rough, knobby, or star-shaped nodule |
| Size Range | Quarter-inch to over five feet across |
| State Rock | Oregon State Rock (designated 1965) |
⛏️ How to Find & Dig Them
- Tool Kit: Digging for thundereggs requires a small rock pick, a chisel, gloves, and buckets to carry your finds.
- Spotting: Look for spherical, potato-shaped rocks with a rough, knobby, or star-shaped exterior.
- Private Ranches: Many rockhounds visit commercial rock ranches (such as the well-known Richardson's Rock Ranch in Madras) where visitors can dig for a fee and use on-site lapidary saws to cut their treasures open.
- Public Lands: You can also search on Bureau of Land Management (BLM) public lands, such as the Succor Creek State Natural Area, though regulations and limits may apply.
🤯 Fun Facts
- Thundereggs can range in size from a quarter-inch to as large as five feet across.
- The world's largest thunderegg, weighing 1.75 tons, is housed at the Rice Northwest Museum of Rocks and Minerals in Hillsboro, Oregon.
- Oregon officially designated the thunderegg as its state rock in 1965 — a testament to their cultural and geological significance.
Ref: 0174 (For my use only)