mineral
Quartz Geode
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale), Color: White, gray, or clear crystal interior with a dark outer rind, Luster: Vitreous/glassy crystals with a dull/earthy exterior, Crystal Structure: Trigonal/Hexagonal, Cleavage: None/Conchoidal fracture
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Physical properties
Hardness: 7 (Mohs scale), Color: White, gray, or clear crystal interior with a dark outer rind, Luster: Vitreous/glassy crystals with a dull/earthy exterior, Crystal Structure: Trigonal/Hexagonal, Cleavage: None/Conchoidal fracture
Formation & geological history
Formed in hollow cavities of volcanic or sedimentary rocks where mineral-rich water seeps in over thousands of years, precipitating crystals onto the interior walls.
Uses & applications
Primarily used for decorative home decor, crystal collecting, and educational purposes. Some high-clarity minerals from geodes are used in jewelry.
Geological facts
The word geode comes from the Greek word 'Geoides' meaning earth-like. Unlike a vug, which is a cavity in rock, a geode is a separate structure that can be removed from its host rock intact.
Field identification & locations
Identify in the field by looking for rounded, bumpy, potato-like nodules that feel lighter than solid rocks of the same size. Commonly found in deserts and volcanic ash beds worldwide.
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