mineral
Quartz Geode
Silicon Dioxide (SiO2)
Mohs hardness 7, transparent to translucent white/colorless crystals, vitreous (glassy) luster, trigonal crystal system, conchoidal fracture, specific gravity 2.65
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Physical properties
Mohs hardness 7, transparent to translucent white/colorless crystals, vitreous (glassy) luster, trigonal crystal system, conchoidal fracture, specific gravity 2.65
Formation & geological history
Formed in cavities within sedimentary or volcanic rocks where silica-rich groundwater gradually precipitates quartz crystals over thousands to millions of years.
Uses & applications
Popular for display specimens, lapidary projects, crystal healing collections, educational gifts, and jewelry.
Geological facts
Geodes look like ordinary, unremarkable stones on the outside, but when cracked open, they reveal a hollow cavity lined with sparking crystals.
Field identification & locations
Identify by its round outer shell and hollow interior lined with sharp, pointed quartz crystal terminations that can scratch glass (hardness 7). Commonly found in Morocco, Mexico, Brazil, and the Midwestern US (Iowa, Illinois).
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