Agate Thunder EggA Thunder Egg is a nodule like rock, similar to a filled geode, that formed within volcanic ash layers. They are usually composed of quartz, agate, opal, and or visibly crystalline quartz like Agate. It is a grounding, soothing and calming stone that creates emotional and intellectual balance. This stone will aid in cantering and stabilizing energy. It also promotes self acceptance and confidence, encouraging the speaking of ones own truth.