sedimentary
Geode (Unopened)
Crystalline Quartz Geode (SiO2)
Hardness: 7 (Mohs scale), Color: Dull gray to tan exterior with a rough, bumpy texture, Luster: Earthy exterior, Crystal Structure: Hexagonal (interior crystals), Specific Gravity: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: Dull gray to tan exterior with a rough, bumpy texture, Luster: Earthy exterior, Crystal Structure: Hexagonal (interior crystals), Specific Gravity: 2.65
Formation & geological history
Formed in the cavities of sedimentary or volcanic rocks. Over millions of years, mineral-rich water seeps through the porous shell, depositing crystals (usually quartz or calcite) on the interior walls.
Uses & applications
Used primarily for collector specimens, interior decor, education, and lapidary work. Highly valued by hobbyists who enjoy cracking them open to reveal crystals.
Geological facts
The word geode comes from the Greek word 'geoides,' meaning 'earth-like.' While they look like ordinary rocks on the outside, they can contain beautiful amethyst, citrine, or clear quartz inside.
Field identification & locations
Identify in the field by looking for unusually round or oval-shaped nodules that feel lighter than regular rocks of the same size. Commonly found in desert environments like the Southwestern US, Mexico, and Brazil.
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