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What are Thundereggs?

natural thunderegg

Thunderegg Geological Structure

A thunderegg is a sphere-like geological structure which forms in lava flows.

The centre eventually splits to form a cavity which over time, fills with either chalcedony, agate, opal, jasper or quartz.  When the ordinary looking outer rock is broken open it reveals minerals within a self-contained centre.

Article Photo

The thunderegg in our photo is courtesy of Stan Celestian. The image is clickable and redirects to the original non-compressed photo.

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