Description
Thunder eggs are products of circulating hot fluids rich in silica...circulating in hot volcanic ash. What amazed me about this thunder egg was the fact that a fault offset was quite evident. The ellipsoid had a conspicuous offset, which can be seen in the exterior views of this rock. I was ecstatic. How often do you find a faulted thunder egg? ;I could imagine the beautiful agate that would be inside, and I could “see” a situation where the delicate laminations would be offset along the fault. I could imagine that the agate would be crushed along the fault. I worked out a price with the owner (he sold it to me on per-pound basis), and I had it sawed and polished. The interior of the thunder egg lacked all signs of faulting. I cannot figure out how to explain the combination of faulting on the outside, and no faulting on the inside. Perhaps the original egg was an empty egg with a chalcedony outer wall. Perhaps the hollow interior began filling with gel-like silica. While the stiff outer rind of the wall of the thunder egg was being faulted, the interior of the shell was still filling with a gel-like goo, which was impervious to faulting and displacement. Perhaps the gel-like silica simply slowly filled the chamber. I still have not focused on the curves and bends of the agate laminae, and whether any relate in twists and turns to the faulting evident on the outside. ;I like this rock a lot, but I wish I could work out its history. ;Hope someone listening out there can help me.
Whereabouts
In ~2002 I went to a rock shop on Dodge Avenue in Tucson, Arizona. After looking around a while inside, I learned that there were a lot of specimens lying around in the backyard. There I spotted this thunder egg in its native uncut form.
Age & Formation
Unknown.