6 to 8 million years ago, volcanic activity in Western Utah deposited an igneous rock called rhyolite. Trapped gases formed pockets in the rhyolite, which eventually became lined with chalcedony and quartz from groundwater. Most Dugway Geodes fluoresce a lime green color due to minute amounts of a secondary mineral that bonded with the quartz when it was growing.
Dimensions in inches: 5"L x 5"W
Approximate burn time: 4hrs