mineral
Quartz Geode
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale), Color: Clear to white crystals within a gray/brown host rock, Luster: Vitreous to waxy, Crystal Structure: Hexagonal (trigonal), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: Clear to white crystals within a gray/brown host rock, Luster: Vitreous to waxy, Crystal Structure: Hexagonal (trigonal), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed in volcanic or sedimentary rock cavities where mineral-rich groundwater precipitates crystals over thousands of years. Often found in basaltic lavas or limestones.
Uses & applications
Primary use is for mineral collecting, decorative display pieces, and educational purposes. Historically used for making jewelry components.
Geological facts
Geodes are hollow, subspherical rocks containing a lining of crystals. You cannot tell if a rock is a geode from the outside; only cracking it open reveals the internal treasure.
Field identification & locations
Identify in the field by looking for round, lumpy rocks that feel lighter than expected for their size. Common locations include Morocco, Brazil, Mexico, and Iowa (USA).
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