sedimentary
Quartz Geode
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale); Color: White, gray, or clear crystals; Luster: Vitreous to waxy; Crystal structure: Hexagonal (trigonal); Cleavage: None; Specific gravity: 2.65
- Hardness
- 7 (Mohs scale)
- Color
- White, gray, or clear crystals
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 (Mohs scale); Color: White, gray, or clear crystals; Luster: Vitreous to waxy; Crystal structure: Hexagonal (trigonal); Cleavage: None; Specific gravity: 2.65
Formation & geological history
Formed as hollow cavities in sedimentary or volcanic rock that are filled by the slow precipitation of mineral-rich water over millions of years.
Uses & applications
Primarily used for decorative purposes, collecting, educational specimens, and metaphysical uses.
Geological facts
The word geode comes from the Greek word 'Geoides' meaning earth-like. Unlike a vug, which is a cavity in a rock vein, a geode is a separate, rounded structure that can be removed from the host rock intact.
Field identification & locations
Identify by its rounded exterior and hollow interior lined with crystals. Common in limestone deposits such as the Keokuk region of the Midwestern USA, or volcanic regions in Brazil and Mexico.
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