mineral
Quartz Geode
Silicon Dioxide (SiO2)
Hardness 7 on Mohs scale; color ranges from clear to white drusy crystals; vitreous/glassy luster; trigonal crystal system; no cleavage with conchoidal fracture; specific gravity ~2.65.
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Physical properties
Hardness 7 on Mohs scale; color ranges from clear to white drusy crystals; vitreous/glassy luster; trigonal crystal system; no cleavage with conchoidal fracture; specific gravity ~2.65.
Formation & geological history
Formed in cavities within volcanic or sedimentary rocks where mineral-rich water precipitates quartz micro-crystals over millions of years.
Uses & applications
Popular as decorative display specimens, educational items, lapidary projects, and collector pieces.
Geological facts
Geodes often look like ordinary, unremarkable rounded stones from the outside, but cracking them open reveals brilliant sparkling crystal cavities inside.
Field identification & locations
Identified by the rough chalcedony or limestone exterior shell with a hollow cavity lined with sparkling quartz druzy crystals. Common in Morocco, Brazil, Mexico, and the Midwestern United States.
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Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Schist
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Metamorphic
Sandstone with Mineral Veining or Crust
Sedimentary Sandstone (mostly SiO2 with Fe2O3 tinting)
sedimentary
Potassium Feldspar (Orthoclase)
Orthoclase (KAlSi3O8)
mineral
Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral
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Nephrite
Mineral/Rock