mineral
Quartz Geode
Crystalline Silicon Dioxide (SiO2) in a Geodic Concretion
Hardness: 7.0 Mohs; Color: White to colorless; Luster: Vitreous/glassy; Structure: Hexagonal crystals; Cleavage: None/Conchoidal fracture; Specific gravity: 2.65
- Hardness
- 7
- Color
- White to colorless
- Luster
- Vitreous/glassy
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Physical properties
Hardness: 7.0 Mohs; Color: White to colorless; Luster: Vitreous/glassy; Structure: Hexagonal crystals; Cleavage: None/Conchoidal fracture; Specific gravity: 2.65
Formation & geological history
Formed in cavites of sedimentary or volcanic rock. Groundwater containing dissolved minerals seeps into hollow spaces, cooling or evaporating to precipitate crystal layers over thousands to millions of years. Commonly associated with Cretaceous or Mississippian periods.
Uses & applications
Home decor, education/science kits, lapidary art, metaphysical collecting, and small jewelry accents.
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 separable, discrete structure.
Field identification & locations
Identified by a round or egg-shaped exterior with a bumpy or 'cauliflower' texture. They feel lighter than solid rocks of similar size due to the hollow interior. Commonly found in deserts (Sahara) and riverbeds in the Midwestern USA.
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Other mineral specimens
Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Sandstone with Mineral Veining or Crust
Sedimentary Sandstone (mostly SiO2 with Fe2O3 tinting)
sedimentary
Schist
Schist
Metamorphic
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral
Nephrite Jade
Nephrite
Mineral/Rock