sedimentary

Quartz Geode

Silicon Dioxide (SiO2) within a geode

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale), Color: White to translucent clear/gray, Luster: Vitreous to greasy, Crystal structure: Hexagonal (trigonal), Cleavage: None/Conchoidal fracture, Specific gravity: 2.65

Identified April 12, 2026More sedimentary →

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Physical properties

Hardness: 7 (Mohs scale), Color: White to translucent clear/gray, Luster: Vitreous to greasy, Crystal structure: Hexagonal (trigonal), Cleavage: None/Conchoidal fracture, Specific gravity: 2.65

Formation & geological history

Formed in sedimentary or volcanic rock cavities when mineral-rich water precipitates crystals inside hollow spaces over millions of years. Common in Mississippian and Devonian age strata (300-400 million years ago).

Uses & applications

Primarily used as decorative display specimens, for crystal healing collecting, and sometimes lower-grade material is used for jewelry (cabochons or drusy slabs).

Geological facts

Geodes are often indistinguishable from ordinary rocks on the outside. The Keokuk geode is the state rock of Iowa and is world-famous for its high concentration of quartz-filled geodes.

Field identification & locations

Identify in the field by looking for unusually light, round nodules that have a bumpy, 'cauliflower' exterior. They sound hollow when tapped. Commonly found in riverbeds and limestone outcrops.