mineral
Quartz Geode (River Cobble)
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale); Color: White, tan, or clear crystals; Luster: Vitreous to waxy; Crystal structure: Hexagonal/Trigonal (microcrystalline or drusy); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 7 (Mohs scale)
- Color
- White, tan, or clear crystals
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 (Mohs scale); Color: White, tan, or clear crystals; Luster: Vitreous to waxy; Crystal structure: Hexagonal/Trigonal (microcrystalline or drusy); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed by mineral-rich groundwater precipitating silica into hollow cavities within sedimentary or volcanic host rocks. Often found as rounded nodules in riverbeds after the host rock has eroded away.
Uses & applications
Primary use for decorative display, crystal collecting, metaphysical purposes, and educational specimens.
Geological facts
Geodes are virtually indistinguishable from regular rocks on the outside until cracked open to reveal the crystal cavity within. This specimen shows a drusy quartz lining within a weathered sedimentary exterior.
Field identification & locations
Identify by looking for rounded, lumpy 'cauliflower' textures on the surface and a lighter-than-expected weight for its size. Commonly found in gravel bars of ancient riverbeds or limestone deposits.
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