sedimentary

Geode

Crystalline Quartz in Sedimentary Matrix (SiO2)

Hardness: 7 (inner crystals); Color: dark brown exterior with white/translucent interior crystals; Luster: dull exterior, vitreous interior; Structure: Amorphous or microcrystalline exterior with macrocrystalline interior.

Hardness: 7 (inner crystals)
Color: dark brown exterior with white/translucent interior crystals
Luster: dull exterior, vitreous interior

Identified July 14, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed via the precipitation of mineral-rich water within a cavity in sedimentary or volcanic rock over millions of years, typically found in limestone or volcanic ash deposits.

Uses & applications

Used primarily for geological study, home decor, energy healing/metaphysical practices, and as a popular collector specimen for hobbyists.

Geological facts

A geode is essentially a 'rock bubble.' While the outside looks like a common pebble or nodule, the hollow interior contains a world of crystals. The word geode comes from the Greek word 'Geoides' meaning earth-like.

Field identification & locations

Identify in the field by looking for rounded, lumpy nodules that feel lighter than they look (indicating a hollow center). Common in desert regions or areas with limestone bedrock.

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Cone-in-cone structure (Limestone)

Cone-in-cone structure (Secondary Sedimentary Structure)

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Sandstone

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Sandstone Grain

Clastic Sedimentary Rock Grain (SiO2 dominated)

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