mineral

Quartz Geode

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale); Color: White, clear, or milky crystals inside a tan/brown rind; Luster: Vitreous (glassy) internally, earthy externally; Crystal structure: Hexagonal/trigonal; no cleavage; Conchoidal fracture.

Hardness: 7 (Mohs scale)
Color: White, clear, or milky crystals inside a tan/brown rind
Luster: Vitreous (glassy) internally, earthy externally

Identified June 2, 2026More mineral →

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Physical properties

Formation & geological history

Formed in hollow cavities within sedimentary or volcanic rock. Mineral-rich groundwater seeps into gas bubbles (vesicles) or solution cavities, precipitating crystals over millions of years along the interior walls.

Uses & applications

Primarily used for decorative purposes, mineral collecting, education, and by some as metaphysical healing stones. Large, high-quality geodes can be high-end interior design pieces.

Geological facts

Geodes are often called 'thunder eggs' when they are solid or filled with agate. The state of Iowa has designated the geode as its official state rock.

Field identification & locations

Identify by the rough, cauliflower-like exterior and hollow center filled with crystals. Often found in limestone or shale beds in regions like the midwestern United States, Mexico, and Brazil.