mineral
Quartz Geode
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs), Color: Clear/White crystals inside a grey/brown druse, Luster: Vitreous (glassy), Structure: Trigonal/Hexagonal crystals, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
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Physical properties
Hardness: 7 (Mohs), Color: Clear/White crystals inside a grey/brown druse, Luster: Vitreous (glassy), Structure: Trigonal/Hexagonal crystals, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed in cavities of volcanic or sedimentary rock when mineral-rich groundwater precipitates silica over thousands of years. Common in basaltic lava flows and limestone beds.
Uses & applications
Mainly used for decorative purposes, gemstone collecting, metaphysical jewelry, and education in geology.
Geological facts
The word 'Geode' comes from the Greek word 'Geoides' meaning earth-like. They look like ordinary rocks on the outside but contain hollow cavities lined with crystals.
Field identification & locations
Identify in the field by looking for rounded, light-weight nodules that feel hollower than solid rocks. Common in Brazil, Uruguay, Mexico, and the U.S. (Iowa/Oregon).
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