June 17, 2016

Thundereggs

A thunderegg (or thunder egg) is a nodule-like rock, similar to a filled geode, that is formed within 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. A jasper thunderegg from White Fir Springs, Oregon A […]

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