sedimentary

Quartz Geode

Silicon Dioxide (SiO2) in a Secondary Formation

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale), Color: White/Translucent internal crystals with tan exterior, Luster: Vitreous/Glassy interior, dull exterior, Crystal Structure: Trigonal, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Identified April 20, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed as hollow cavities in sedimentary rock (often limestone) that are filled with mineral-rich hydrothermal fluids over thousands of years. The crystals grow inward from the walls of the cavity.

Uses & applications

Primarily used for geological education, home decor, and mineral collecting. Occasionally used for metaphysical or ornamental purposes.

Geological facts

Geodes are often called 'thunder eggs' when they are completely solid. They can range in size from tiny pebbles to massive caverns that a person can walk inside. The white crystals inside this specimen are common quartz, the most abundant mineral on Earth's crust.

Field identification & locations

Identify in the field by looking for rounded, bumpy, lighter-than-expected nodules within limestone or volcanic ash deposits. A 'rattle' when shaken can indicate loose internal crystals. Common locations include Morocco, Mexico, and the Midwestern United States (Keokuk region).