sedimentary
Quartz Geode
Silicon Dioxide (SiO2) in sedimentary host rock
Hardness: 7 (Mohs scale) for crystals; Color: Clear to white crystalline interior, tan/brown exterior rind; Luster: Vitreous (glassy) crystals to earthy exterior; Crystal Structure: Hexagonal; Cleavage: None/Conchoidal fracture.
- Hardness
- 7 (Mohs scale) for crystals
- Color
- Clear to white crystalline interior, tan/brown exterior rind
- Luster
- Vitreous (glassy) crystals to earthy exterior
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Physical properties
Hardness: 7 (Mohs scale) for crystals; Color: Clear to white crystalline interior, tan/brown exterior rind; Luster: Vitreous (glassy) crystals to earthy exterior; Crystal Structure: Hexagonal; Cleavage: None/Conchoidal fracture.
Formation & geological history
Formed as secondary structures within sedimentary or volcanic rocks. They begin as hollow cavities in the rock (bubbles or rotted organic matter) which are filled over millions of years by mineral-rich water precipitating crystals inward.
Uses & applications
Primarily used for geological education, home decor, metaphysical collection, and lapidary art including bookends and jewelry slices.
Geological facts
Geodes are unique because they are hollow, though some, like this one, can be nearly solid (often called 'nodules' or 'solid geodes' when entirely filled). The word 'geode' comes from the Greek word 'Geoides' meaning 'earth-like'.
Field identification & locations
Identify by the rough, cauliflower-like exterior and hollow or crystalline core. Commonly found in limestone deserts or volcanic ash beds. Collectors look for pieces that feel lighter than they look (indicating a hollow center).
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