mineral
Quartz Geode
Silicon Dioxide (SiO2)
Hardness: 7 Mohs; Color: White/Clear; Luster: Vitreous to greasy; Crystal Structure: Trigonal (hexagonal prisms inside cavity); Cleavage: None; Specific Gravity: 2.65
- Hardness
- 7 Mohs
- Color
- White/Clear
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 7 Mohs; Color: White/Clear; Luster: Vitreous to greasy; Crystal Structure: Trigonal (hexagonal prisms inside cavity); Cleavage: None; Specific Gravity: 2.65
Formation & geological history
Formed as secondary structures in sedimentary or volcanic rocks. Mineral-rich waters seep into cavities (gas bubbles or fossil openings), precipitating quartz crystals over thousands of years.
Uses & applications
Primarily used for decorative purposes, crystal healing, educational science kits, and as collector specimens.
Geological facts
The word geode comes from the Greek word 'geodes' meaning earth-like. No two geodes are exactly alike inside, making each a unique natural time capsule.
Field identification & locations
Identify by looking for rounded, cauliflower-like exterior nodules that feel lighter than solid rocks. Common in Morocco, Brazil, and the US Midwest (Iowa, Indiana).
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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