Geodes and Thundereggs from around the world!

Geodes are hollow rocks with crystals grown inside them! Classic localities are found in Illinois, Iowa, Indiana and outside the US such as Mexico and Brazil. Most geodes are sedimentary, while thundareggs are volcanic. 

Thundareggs are solid balls of rock that have chalcedony agate and sometimes crystals in side. Thundareggs are formed very differently than geodes.