13 Fascinating Facts About Geodes

Fossil hunting and geode hunting have a lot in common. To the trained eye, in the right location, fossil-containing rocks are quite easy to spot even before they're split open. Trapped in sedimentary rock, fossils can sometimes cause geodes to form too. Occasionally, the original fossil may weather away over time, leaving behind a cavity in which a geode can begin to crystallize. Very rarely though, something more exceptional can happen; under the right conditions, fossils themselves can become geodized, with shining crystals forming inside them.

In 2022, the South China Morning Post reported on a set of geodes found in Anhui Province, Eastern China, which formed inside fossilized dinosaur eggs. One of them was broken open, revealing a set of white quartz crystals inside. Most remarkably of all, the eggs themselves were laid by a previously unknown species of dinosaur, now dubbed Shixingoolithus qianshanensis. The geode eggs are just a few of the numerous fossil dinosaur eggs that have been unearthed by paleontologists all across China, but they're certainly the most dramatic.

This wasn't the first time geodized fossil eggs have been discovered either. Previously, a set of fossil crocodile eggs at the Smithsonian Museum were found to have crystallized into geodes. Elsewhere, a titanosaur egg unearthed in Mongolia in 2011 was also discovered to be a geode, filled with calcite crystals.

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