Thunder Egg
A variety of Rhyolite
What is Thunder Egg?
The Thunder Egg is a geode-like structure of different minerals, usually in crystalline forms, layered together into a solid structure. The outside is normally an ordinary dull gray or brown rock over a layer of brown or red rhyolite, but the inside can contain concentric rings and layers of quartz crystal, chalcedony, agate, and even opal.
Market Value Factors
Pricing varies for every rock and mineral, so use these universal factors to gauge Thunder Egg before comparing listings or appraisals.
Size & Weight
Larger, intact specimens usually command higher prices.
Rarity & Demand
Scarce material or popular varieties sell at a premium.
Condition & Finish
Chips, repairs, and heavy wear lower value; clean prep helps.
Treatment & Provenance
Untreated specimens with documented locality are prized.
Where to Find Thunder Egg
RockHoundR, the free-to-download rockhounding map from the Ruby Glint team, shows where collectors find thunder egg in the US, with land-access notes for BLM land and national forests. Collecting is banned in national parks.
See where to find thunder eggAlways check the local rules and get the landowner's permission before you collect.
Key Characteristics
Composition of Thunder Egg
Rhyolite, Agate
More Images
Quick Facts
Physical Properties
- Hardness (Mohs)
- 6 - 7
- Rock tumbling
- With care
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Thunder Egg FAQs
How do I identify Thunder Egg?
Thunder Egg can be identified by its hardness of 6 - 7 on the Mohs scale. Look for these key characteristics when examining specimens.
How hard is Thunder Egg?
Thunder Egg has a hardness of 6 - 7 on the Mohs scale. This gives it moderate hardness.
What is the composition of thunder egg of Thunder Egg?
Rhyolite, Agate