mineral

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: white to creamy translucent with iron-staining; Luster: Vitreous to waxy; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 on Mohs scale
Color: white to creamy translucent with iron-staining
Luster: Vitreous to waxy

Identified July 9, 2026More mineral →

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Physical properties

Formation & geological history

Formed in cavities (vugs) within sedimentary or volcanic rock. Mineral-rich groundwater precipitates silica over long periods, often starting with a chalcedony rind and ending with macro-crystalline quartz centers.

Uses & applications

Primarily used for decorative purposes, collecting, and educational geological specimens. High-purity quartz is also used in electronics and glass-making.

Geological facts

Geodes are essentially 'rock bubbles' that formed millions of years ago. This specific specimen shows a botryoidal or crystalline quartz center surrounded by a more massive chalcedony layer.

Field identification & locations

Identify by looking for a rounded exterior with a hollow or crystal-filled interior. Often found in limestone or shale beds. Common in the Midwestern United States (e.g., Keokuk geodes).