sedimentary

Quartz Geode

SiO2 (Silicon Dioxide)

Hardness: 7 on Mohs scale; Color: typically white, clear, or grey in the interior; Luster: vitreous to waxy; Structure: cryptocrystalline or microcrystalline cavity lining; Cleavage: none (conchoidal fracture).

Hardness: 7 on Mohs scale
Color: typically white, clear, or grey in the interior
Luster: vitreous to waxy

Identified July 5, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed via the precipitation of mineral-rich groundwater in cavities within sedimentary rocks or volcanic voids. As mineral-laden water seeps through the porous exterior, crystals grow inward over millions of years.

Uses & applications

Primarily used for educational collecting, home decor, and spiritual/metaphysical purposes. Higher quality specimens are cut and polished for jewelry.

Geological facts

The name 'geode' comes from the Greek word 'geodes' meaning 'earth-like'. No two geodes are exactly alike, and they are like geological time capsules containing minerals from prehistoric eras.

Field identification & locations

Identify in the field by looking for round or egg-shaped nodules that feel unexpectedly light for their size (indicating a hollow center). Common in limestone areas of the Midwest USA, Brazil, and Mexico.