ThunderEgg- Rock of the day- Geology, Lapidary, Rockhounding.

A thunderegg is a type of rock similar to a geode but formed in a rhyolitic lava flow and found only in areas of volcanic activity. Thundereggs are rough spheres, most about as big as a baseball. They look uninteresting on the outside, but slicing them in half may reveal highly attractive patterns and colors valuable in jewelry.

Two stories on how they got their name:

1-Incidentally, the word, “thunderegg,” which includes both nodules and geodes, appears to have first been used by the Indians of central Oregon. It is said that they believed that Thunder Spirits living in volcanoes sometimes fought battles in which they hurled thunder, lightning, and stone “eggs” at each other. Perhaps those Indians knew what they were talking about, because parts of Oregon also offer spectacular geodes and nodules!

2-According to native legend, the Thunder Spirits lived at the highest reaches of Mount Hood and Mount Jefferson, and when they became angry at each other, they threw these spherical rocks at each other.

They are the state rock of the American state of Oregon.