thunderegg
Agate-filled volcanic rock
A thunderegg is a round, rough-looking rock that reveals colorful crystalline patterns—usually agate or chalcedony—when cut open.
Found in volcanic ash deposits, the plain exterior conceals spectacular interior formations.
The name supposedly comes from Native American legend about thunder spirits hurling the stones.
We collected thundereggs in the Oregon desert.
Banded semiprecious stone
- chalcedonyTranslucent microcrystalline silica variety
- quartzCrystalline silicon dioxide
- opalHydrated silica gemstone
- jasperOpaque colored quartz
silica · crystal · druzy · geode · matrix · rind · cortex · shell
Pale volcanic igneous rock
- lavaErupted liquid stone
- volcanicOf fiery mountain origin
- silicaSilicon dioxide compound
- noduleRounded small lump
vesicle · cooling · precipitation · infilling · concentric · banding · cavity · void
agate
Banded semiprecious stone
- chalcedonyTranslucent microcrystalline silica variety
- quartzCrystalline silicon dioxide
- opalHydrated silica gemstone
jasper · silica · crystal · druzy · geode · matrix · rind · cortex · shell · core
rhyolite
Pale volcanic igneous rock
nodule · vesicle · cooling · precipitation · infilling · concentric · banding · cavity · void · pyroclastic
Oregon
Northwestern U.S. state
Mexico · Argentina · Australia · lapidary · rockhound · specimen · locality · deposit · claim · excavation
specimen
Individual for examination
polished · cut · slab · bookend · sphere · tumbled · rockhound · trade · value · rare
thundereggfossil
Preserved ancient organism
amber · petrified wood · coprolite · ammonite · sedimentary rock