sedimentary
Quartz Geode Fragment
Silicon dioxide (SiO2) within a nodule
Hardness: 7 on Mohs scale; Color: white to translucent crystals; Luster: Vitreous; Crystal Structure: Trigonal/Hexagonal; Cleavage: None/Conchoidal fracture.
- Hardness
- 7 on Mohs scale
- Color
- white to translucent crystals
- Luster
- Vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: white to translucent crystals; Luster: Vitreous; Crystal Structure: Trigonal/Hexagonal; Cleavage: None/Conchoidal fracture.
Formation & geological history
Formed as hollow cavities in sedimentary rock (typically limestone or shale) through the deposition of minerals from hydrothermal fluids over millions of years.
Uses & applications
Primarily used for educational collections, home decoration, and metaphysical purposes. Larger, high-quality geodes are used in specimen collecting.
Geological facts
Geodes are often called 'thunder eggs' when they are solid. No two geodes are exactly alike, and the interior can contain a variety of different minerals like calcite or chalcedony.
Field identification & locations
Look for rounded, potato-like rocks that feel lighter than they look. In the field, shaking a geode can sometimes reveal a hollow sound. Common in Morocco, Mexico, and the Midwestern United States.
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