sedimentary
Geode (Unopened)
Crystalline Quartz or Chalcedony filled Geode (SiO2)
AI-generated identification · may be incorrectHardness: 7 (Mohs scale), Color: Brownish or grey exterior with white or tan hints, Luster: Dull or earthy on exterior, Crystal Structure: Hexagonal (interior), Cleavage: None, Specific Gravity: 2.60-2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: Brownish or grey exterior with white or tan hints, Luster: Dull or earthy on exterior, Crystal Structure: Hexagonal (interior), Cleavage: None, Specific Gravity: 2.60-2.65
Formation & geological history
Formed in sedimentary rock cavities (such as limestone) through mineral precipitation from groundwater over millions of years. Common in Mississippian and Devonian strata.
Uses & applications
Geological collecting, lapidary arts, metaphysical/decorative purposes, and educational specimens.
Geological facts
Geodes look like ordinary round rocks on the outside but contain hollow centers filled with crystals. The word 'geode' comes from the Greek word 'geoides' meaning earth-like.
Field identification & locations
Identify by its unusually light weight relative to its size and rounded, bumpy, cauliflower-like exterior. Common in the Midwest USA (Keokuk region) and Brazil.
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