mineral
Quartz Geode
Silicon Dioxide (SiO2)
Hardness: 7 on Mohs scale; Color: Colorless to white/opaque; Luster: Vitreous to greasy; Crystal Structure: Hexagonal (trigonal); Cleavage: Indistinct/Conchoidal fracture; Specific Gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Colorless to white/opaque
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 7 on Mohs scale; Color: Colorless to white/opaque; Luster: Vitreous to greasy; Crystal Structure: Hexagonal (trigonal); Cleavage: Indistinct/Conchoidal fracture; Specific Gravity: 2.65
Formation & geological history
Formed as secondary mineral precipitates in hollow cavities (vugs) within igneous or sedimentary rocks. Silica-rich hydrothermal fluids seep into the cavity, slowly crystallizing over thousands of years.
Uses & applications
Primarily used for decorative purposes, collectors' specimens, and metaphysical practices. High-purity quartz is used in electronics and glass-making.
Geological facts
The word geode comes from the Greek word 'Geoides' meaning earth-like. Unlike solid nodules, geodes are hollow, and this specimen represents a fragment of a larger druzy cavity.
Field identification & locations
Identify by its vuggy, crystalline interior contrasted against a rough, weathered outer rind. Often found in limestone or volcanic ash beds. Look for round or egg-shaped stones that feel lighter than they look.
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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
Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Nephrite Jade
Nephrite
Mineral/Rock