Opal Jasper Thunderegg

Opal Jasper Thunderegg Slab, mined in Northeastern Oregon, USA. 

How is a thunder egg formed?

A thunderegg is a nodule-like rock, similar to a filled geode, formed within rhyolitic volcanic ash layers. Thundereggs are rough spheres, most about the size of a baseball—though they can range from a little more than a centimeter to over a meter across. They usually contain centers of chalcedony which may have been fractured, followed by deposition of agate, jasper, or opal, either uniquely or in combination. Also frequently encountered are quartz and gypsum crystals, as well as various other mineral growths and inclusions.

Thundereggs usually look like ordinary rocks on the outside, but slicing them in half and polishing them may reveal intricate patterns and colors. A characteristic feature of thundereggs is that (like other agates) the individual beds they come from can vary in appearance, though they can maintain a certain specific identity within them. In the United States, Oregon is one of the most famous Thunderegg locations.

Thundereggs are grounding, soothing and calming stones that create emotional, physical, and intellectual balance. Thundereggs will aid with centering and stabilizing physical energy.  It’s also believed that thundereggs enhance mental functions, improve concentration, perception, and analytical abilities.