Thunder eggs come from cavities in volcanic rocks that have filled in with agate, jasper, opal or other materials. This thunder egg from Richardson’s Ranch filled in with blue agate.
![richardsons-ranch-thunderegg](https://i0.wp.com/stonetimbers.com/wp-content/uploads/2024/02/richardsons-ranch-thunderegg.jpg?resize=1024%2C1024&ssl=1)
Thunder eggs come from cavities in volcanic rocks that have filled in with agate, jasper, opal or other materials. This thunder egg from Richardson’s Ranch filled in with blue agate.