geode

American  

[jee-ohd] / ˈdʒi oʊd /

noun

1. a hollow concretionary or nodular stone often lined with crystals.

2. the hollow or cavity of this.

3. any similar formation.

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geode British  

/ dʒɪˈɒdɪk, ˈdʒiːəʊd /

noun

1. a cavity, usually lined with crystals, within a rock mass or nodule

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geode Scientific  

/ jē′ōd′ /

1. A small, hollow, usually rounded rock lined on the inside with inward-pointing crystals. Geodes form when mineral-rich water entering a cavity in a rock undergoes a sudden change in pressure or temperature, causing crystals to form from the solution and line the cavity's walls.

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Other Word Forms

• geodal adjective
• geodic adjective

Etymology

Origin of geode

1670–80; < French géode < Latin geōdēs < Greek geṓdēs earthlike. See geo-, -ode ¹

Explanation

On the outside, a geode looks like an ordinary rock, but when you break a geode open, it's full of crystals. Geodes are hollow rock formations with minerals, often quartz crystals, massed inside. A geode forms when minerals settle into a hollow in the earth (like an animal burrow) or inside volcanic rock bubbles. First, a hard shell is formed, and then the minerals grow toward the center of the geode, often forming crystals in the process. The Greek root, geodes, means "earth-like."

Example Sentences

Looking like a glittering cosmic geode, a trio of dazzling stars blaze from the hollowed-out cavity of a reflection nebula in this new image from NASA's Hubble Space Telescope.

From Science Daily • May 15, 2024

“This place is as good as it gets,” Losson said recently as he hoisted a small geode filled with quartz crystals.

From Los Angeles Times • Jul. 16, 2023

After every death, Nadia wakes up back in Maxine's cool bathroom with a glowing geode on the door and a gun-shaped door handle.

From Salon • Apr. 16, 2022

The social network also noticed increased searches for ocean nails acrylic, aurora nails and geode nail art.

From Fox News • Jan. 18, 2022

She imagined polishing the dark earth until it was like a geode: shiny, black, and reflective.

From "Boots on the Ground: America's War in Vietnam" by Elizabeth Partridge