mineral
Quartz Geode
Macrocrystalline Quartz (SiO2) within a geode structure
Hardness: 7 on Mohs scale; Color: White to translucent; Luster: Vitreous/Glassy; Structure: Trigonal/Hexagonal crystals lining a cavity; Cleavage: None/Conchoidal fracture; Specific gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- White to translucent
- Luster
- Vitreous/Glassy
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Physical properties
Hardness: 7 on Mohs scale; Color: White to translucent; Luster: Vitreous/Glassy; Structure: Trigonal/Hexagonal crystals lining a cavity; Cleavage: None/Conchoidal fracture; Specific gravity: 2.65
Formation & geological history
Formed in cavities within sedimentary rocks or volcanic flows. Mineral-rich groundwater seeps into a hollow nodule, allowing silica to precipitate and grow crystals inward over thousands of years. Usually associated with Cenozoic to Cretaceous periods.
Uses & applications
Primarily used for geological education, home decor, metaphysical collecting, and jewelry components.
Geological facts
Geodes are often called 'thunder eggs' when they are filled solid. The word geode comes from the Greek word 'Geoides' which means earth-like. Many of the white geodes in this style originate from Morocco or the Tabasco region in Mexico.
Field identification & locations
Identified in the field as round, lumpy nodules with a rough, dull exterior that feel lighter than they look (due to the hollow center). Often found in limestone or volcanic ash beds. Best found by looking for spherical-form debris in washes or stream beds.
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