Geodes primarily form when cavities, created by gas bubbles in lava or dissolved fossils, gradually fill with minerals dissolved in water. These minerals slowly crystallize on the internal walls, ...

Researchers studying amethyst geode formation in Brazil’s lava flows have proposed temperatures below 100 °C. The new study uses similar techniques and includes an additional oxygen isotope.

The “earbuds” that give the formation a modern twist are, in fact, a now grown over dirt road and a oil well, adding an amusing or tragic element to the scene, depending on one’s perspective.

A dazzling twelve-foot-tall example (pictured, in detail, above) greets visitors to the American Museum of Natural History’s newly redesigned Mignone Halls of Gems and Minerals, a showcase of ...

In 2017, researchers going through fossils at the Smithsonian Museum in Washington D.C. stumbled upon 50-million-year-old crocodile eggs that had transformed into geodes filled with quartz crystals.