Thunder Eggs
Thunder eggs are rhyolite nodules — solid, not hollow like a true geode — that formed as gas cavities filled with agate, chalcedony, jasper, or opal. Four sites document them across Oregon, Nevada, and New Mexico, and one, Succor Creek, is considered the signature Oregon locality for the material.
A thunder egg is a rhyolite nodule that formed when gas cavities in volcanic rock filled with agate, chalcedony, jasper, or occasionally opal — solid all the way through, which is what separates it from a true hollow geode even though the two get confused constantly (the site data on this site is careful to keep them distinct, and this page follows that same line). Cracked open, the interior shows a banded or star-shaped pattern that's often invisible from the plain, rounded exterior.
Oregon is the material's best-known home — the state fossil-slash-rock status even reflects it — and Succor Creek State Natural Area is the signature locality documented here. But the same nodule type shows up further afield: Nevada's Rye Patch Reservoir and New Mexico's Rockhound State Park, the park the material's name is literally attached to, both produce it too.
Sites where thunder eggs are documented
| Site | State | Verdict | What's notable there |
|---|---|---|---|
| Succor Creek State Natural Area | Oregon | Allowed | The signature Oregon locality; vivid banded interiors, considered the benchmark for the material |
| Hampton Butte | Oregon | Allowed | Present but limited — smaller and less consistent than Succor Creek's material |
| Rye Patch Reservoir (BLM) | Nevada | Allowed | The primary target at this site; 2–8 inch rhyolite nodules with chalcedony, banded agate, or drusy quartz interiors |
| Rockhound State Park | New Mexico | Allowed | The material the park itself is named for; the site's own notes distinguish these from the park's true hollow geodes |
Verdicts and notes reflect each site's own published page as of this writing. Confirm current rules on the specific Site page before collecting — this table doesn't replace it.
Thunder egg or geode?
A thunder egg is solid rhyolite with an agate, chalcedony, or jasper-filled interior — it looks like an ordinary rounded rock until you cut or crack it open. A true geode is hollow, typically crystal-lined on the inside. The two get lumped together constantly in casual rockhounding conversation, but the sites documented here treat them as genuinely different finds — see this site's separate Geodes material page for the hollow-cavity version.
Where Thunder Eggs Is Documented
Succor Creek State Natural Area
OregonAllowedThe signature Oregon thunder-egg locality; agate, chalcedony, jasper, or opal interiors with vivid banding.
Hampton Butte (BLM)
OregonAllowedPresent in limited numbers — smaller and less consistent than Succor Creek's material.
Rye Patch Reservoir BLM
NevadaAllowedThe primary target at this site; 2–8 inch nodules with chalcedony, banded agate, or drusy quartz interiors.
Rockhound State Park
New MexicoAllowedThe material the park is named for; distinct from the park's true hollow geodes.
Each site’s own page is the source of truth on current rules and limits — this page only gathers what’s already documented there. Verdicts shown reflect that site as a whole, not this material specifically, since a single site can allow one material while restricting another.
Frequently Asked Questions
What is a thunder egg, exactly?
A solid rhyolite nodule formed when a gas cavity in volcanic rock filled with agate, chalcedony, jasper, or occasionally opal. It looks like a plain round rock on the outside — the pattern only shows once it's cut or cracked open.
Where is the best place to find thunder eggs?
Succor Creek State Natural Area in Oregon is the signature locality documented on this site, known for particularly vivid banded interiors. Rye Patch Reservoir in Nevada and Rockhound State Park in New Mexico are the other two sites with strong, well-documented thunder-egg finds.
Is it legal to collect thunder eggs at these sites?
At all four sites documented here, yes, under each site's personal-use collecting rules — but confirm the specific site's page for exact daily limits and any permit requirements before you go, since those details vary by land manager.
Related Materials
Disclaimer
Information is provided for general guidance only. Regulations change frequently. Always verify current rules with the official jurisdiction before relying on this information for legal decisions. Permitted Pursuits is not a substitute for official agency guidance. Report an error.
Last updated: 2026-08-20