sedimentary

Geode (Unopened)

Quartz Geode (SiO2-rich chalcedony/quartz nodule)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale; Color: Grayish-tan, off-white exterior with dark fracture cavities; Luster: Earthy/dull exterior, vitreous internal crystals; Specific Gravity: ~2.6-2.65

Hardness: 6
Color: Grayish-tan, off-white exterior with dark fracture cavities
Luster: Earthy/dull exterior, vitreous internal crystals

Identified July 26, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Grayish-tan, off-white exterior with dark fracture cavities; Luster: Earthy/dull exterior, vitreous internal crystals; Specific Gravity: ~2.6-2.65

Formation & geological history

Formed by chemical precipitation of silica-rich solutions inside gas bubbles (vesicles) in volcanic rock or cavities in sedimentary limestones over millions of years. Often found in riverbeds, desert environments, or weathered limestone formations.

Uses & applications

Popular among rockhounding hobbyists, educational displays, lapidary arts, and decorative polished display pieces once cracked open or sliced.

Geological facts

Unopened geodes are colloquially referred to as 'rattlers' if internal loose crystals shake around, or 'keokuk geodes' if found in the famous Midwest region. The exterior often looks like a plain, lumpy nodule of limestone or chalcedony.

Field identification & locations

Identify by its spherical to oblong shape, lightweight feel relative to size (indicating a hollow interior), and rough exterior surface with potential small fracture lines showing underlying quartz crystals. Commonly found in Iowa, Missouri, Illinois, Indiana, Brazil, and Mexico.