Description
The multi-colored rhyolite minerals are permeated with transparent and opaque lines. If you believe the traditions, these exceptional stones, often called Thundereggs amulet stones, possess immense mystical powers. Original amulet stones with a guarantee of authenticity.
A thunderegg (or donderei) is a lump-like rock, similar to a filled geode, that forms in rhyolitic volcanic ash layers. Thundereggs are rough spheres, most about the size of a baseball—though they can range from less than an inch to over a meter across. They typically contain chalcedony centers that may be fractured, followed by deposition of agate, jasper, or opal, either uniquely or in combination. Quartz and gypsum crystals are also common, as are various other mineral growths and inclusions. Thundereggs typically look like ordinary stones on the outside, but by cutting them in half and polishing them, intricate patterns and colors can be revealed. A characteristic feature of thundereggs is that (like other agates) the individual beds from which they come can vary in appearance, although they may retain a distinct identity within. Thunderegg is not synonymous with geode or agate. A geode is simply a term for a rock with a cavity in it, often with crystal formation/growth. A thunderegg, on the other hand, is a specific geological structure. A thunderegg can be called a geode if it contains a cavity (see illustration of Gehlberg specimen), but not all geodes are thundereggs, as there are many different ways a cavity can form. Similarly, a thunderegg is just one of the forms agate can take.
