sedimentary

Quartz Geode with Chalcedony

Silicon Dioxide (SiO2) in Geode Form

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale); Color: White, gray, tan; Luster: Vitreous to waxy; Crystal structure: Trigonal/Microcrystalline; Cleavage: None; Specific Gravity: 2.65

Hardness: 7 (Mohs scale)
Color: White, gray, tan
Luster: Vitreous to waxy

Identified June 9, 2026More sedimentary →

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Physical properties

Hardness: 7 (Mohs scale); Color: White, gray, tan; Luster: Vitreous to waxy; Crystal structure: Trigonal/Microcrystalline; Cleavage: None; Specific Gravity: 2.65

Formation & geological history

Formed via secondary mineral precipitation in cavities of sedimentary limestone or volcanic ash. Ground water carries dissolved silica into hollow pockets where it cools or evaporates, leaving behind crystalline layers.

Uses & applications

Home decor, geological education, lapidary arts, and mineral collecting. Large, high-quality geodes are often used as statement décor pieces.

Geological facts

The word geode is derived from the Greek word 'Geoides' meaning earth-like. Unlike a vug, which is a cavity in rock, a geode is a self-contained structure that can be separated from its host rock.

Field identification & locations

Identify in the field by looking for rounded, pumpkin-like nodules that feel lighter than other rocks of the same size. Commonly found in desert regions or limestone beds in the Midwest US and Brazil.