Oregon Thundereggs are nodule-like masses usually formed within a rhyolitic lava flow. Silicates such as agate and opal along with other minerals filled pockets in the rhyloite creating egg shaped nodules. Most of the so called eggs are fairly plain banded gemstone. But on occasion other minerals and or crystal structures made for very interesting gemstones.This stone is from the Priday/Richardson deposit. The pendant is 26x17mm (1" x .67") Chain not included.