Dugway Geodes (Thundereggs)

From the Dugway Geode beds located far out in the desert East of Vernon, Juab County, Utah.

So - when does a thunderegg stop being a thunderegg and become a geode? What exactly is the difference? The answer seems to lie in the method of formation, with geodes being formed through a sedimentary process (perhaps why geodes can be much more 'sedate' and calm in appearance), while thundereggs originate from a volcanic one (perhaps hence the more tortured shape of thundereggs!). Going by this formation-based definition, the famous Dugway Geodes certainly fall into the category of thundereggs, in spite of their name. And they look the part as well, with their beautiful and subtle combination of thin violet agate and gleaming crystal. Not to mention the tortured shapes sometimes present in the rock. Taken as thundereggs they make a beautiful and distinctive addition to the family.