Thunderegg
Lapidary material
Also called Thunder egg
About it
Rough, knobby nodules from rhyolite ash beds that hide a star-shaped core of agate, jasper, or opal when sawn open. Oregon's state rock; also found in Germany, Australia, and Mexico.
- Type
- Lapidary material
- Group
- Nodule (volcanic)
- Lustre
- dull, waxy
- Colours
- brown or grey outside; agate, jasper, or opal core
- Transparency
- opaque, translucent
Typical values: real specimens vary. For more, see mindat.org.