sedimentary

Quartz Geode

Silicon Dioxide (SiO2) in Geodic Cavity

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale); Color: White to translucent; Luster: Vitreous/glassy on internal crystals, dull on outer rind; Crystal Structure: Trigonal/Hexagonal; Cleavage: None/Conchoidal fracture.

Hardness: 7 (Mohs scale)
Color: White to translucent
Luster: Vitreous/glassy on internal crystals, dull on outer rind

Identified July 15, 2026More sedimentary →

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Physical properties

Hardness: 7 (Mohs scale); Color: White to translucent; Luster: Vitreous/glassy on internal crystals, dull on outer rind; Crystal Structure: Trigonal/Hexagonal; Cleavage: None/Conchoidal fracture.

Formation & geological history

Formed as secondary mineral deposits in hollow cavities of sedimentary or volcanic rocks. Mineral-rich groundwater seeps into these cavities, slowly precipitating crystals over millions of years.

Uses & applications

Primarily used as decorative display specimens, educational tools in geology, and for lapidary work. Small, clear crystals are sometimes used in jewelry.

Geological facts

The word geode comes from the Greek word 'Geoides' which means earth-like. Unlike vugs, geodes can often be separated from the surrounding host rock as intact nodules or spheres.

Field identification & locations

Identify by the rough, cauliflower-like outer texture and the hollow, crystal-lined interior. Common in regions like the midwestern United States (e.g., Keokuk, Iowa), Morocco, and Brazil.