sedimentary

Geode (Unopened)

Silica-rich Concretion (SiO2)

Hardness: 7 (outer shell), Color: Dull brown or gray exterior with a bumpy/cauliflower texture, Luster: Earthy, Structure: Spherical or subspherical hollow nodule

Luster: Earthy, Structure: Spherical or subspherical hollow nodule

Identified July 20, 2026More sedimentary →

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Physical properties

Hardness: 7 (outer shell), Color: Dull brown or gray exterior with a bumpy/cauliflower texture, Luster: Earthy, Structure: Spherical or subspherical hollow nodule

Formation & geological history

Formed in sedimentary rock cavities (such as limestone) or volcanic ash beds where mineral-rich water precipitates crystals over millions of years.

Uses & applications

Primarily used for educational purposes, mineral collecting, lapidary art, and home decor once cracked open to reveal internal crystals.

Geological facts

The word geode comes from the Greek word 'Geoides' meaning earth-like. Many geodes contain quartz, amethyst, or calcite crystals inside that have never seen light until opened.

Field identification & locations

Identify by its rounded shape, lightweight feel compared to solid rocks of the same size (indicating a hollow center), and distinct 'cauliflower' surface texture.