These geodes come from Juab County, Utah. These unusual and multi-cavity geodes are Utah’s version of Thunder Eggs. 6 to 8 million years ago volcanic activity deposited the extrusive igneous rock Rhyolite. Over time, trapped gasses formed cavities within the Rhyolite. Over millions of years, silica-rich fluids seeped into the cavities and formed these druzy and crystalline quartz lined geodes. 32,000 to 14,000 years ago, ancient Lake Bonneville covered most of western Utah. The lake’s wave activity eroded the geode-bearing Rhyolite and deposited the geodes several miles away in the Dugway geode bed area as lake sediments. Geodes measure 2.5″-3″ x 2.5″-3″. Every geode is unique and may vary from pictured item.