sedimentary
Geode
Silicon dioxide (Quartz/Chalcedony) in carbonate/volcanic host
AI-generated identification · may be incorrectMohs hardness of 7 for quartz crystals, dull exterior crust, vitreous crystal interior, conchoidal fracture.
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Physical properties
Mohs hardness of 7 for quartz crystals, dull exterior crust, vitreous crystal interior, conchoidal fracture.
Formation & geological history
Formed when mineral-rich groundwater deposits silica inside hollow cavities in sedimentary or volcanic rock over millions of years.
Uses & applications
Popular in lapidary work, jewelry, crystal healing, and as decorative collector specimens.
Geological facts
Geodes start as hollow bubbles in rock formed by animal burrows, tree roots, or gas pockets in lava, slowly lining with crystals.
Field identification & locations
Found worldwide in limestone formations and volcanic ash beds; identified by their rounded, bumpy exterior and hollow center.
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