sedimentary
Geode
Quartz / Chalcedony nodule
AI-generated identification · may be incorrectHardness 7 on Mohs scale, grayish exterior with crystalline quartz interior cavity, vitreous luster, trigonal crystal system.
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Physical properties
Hardness 7 on Mohs scale, grayish exterior with crystalline quartz interior cavity, vitreous luster, trigonal crystal system.
Formation & geological history
Formed in hollow spaces in sedimentary or volcanic rocks where silica-rich groundwater deposits mineral crystals over millions of years.
Uses & applications
Used primarily as decorative ornamental items, lapidary art, and collector specimens.
Geological facts
Geodes start as hollow nodules or bubbles in rock, slowly growing interlocking quartz crystals pointing inward toward a void.
Field identification & locations
Identify by a rough, spherical, bumpy outer limestone or basalt shell that reveals sparkling crystals when cracked open.
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