mineral

Quartz Geode

Silicon Dioxide (SiO2)

Hardness of 7 on the Mohs scale, transparent to translucent with a vitreous to greasy luster, hexagonal crystal system, colorless to white, and exhibits conchoidal fracture with no true cleavage.

Identified August 1, 2026More mineral →

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Physical properties

Hardness of 7 on the Mohs scale, transparent to translucent with a vitreous to greasy luster, hexagonal crystal system, colorless to white, and exhibits conchoidal fracture with no true cleavage.

Formation & geological history

Formed in hollow cavities in sedimentary or volcanic rocks where silica-rich groundwater enters and slowly precipitates quartz crystals over thousands to millions of years.

Uses & applications

Used widely in decorative items, lapidary art, crystal healing, collection, and as industrial sources of silica.

Geological facts

Geodes start as bubbles in volcanic rock or animal burrows in sedimentary rock. Over time, mineral-rich groundwater lines the cavity, forming a tough outer shell while inner crystals grow inward toward the center.

Field identification & locations

Easily identified by its rough, rounded exterior shell coupled with an inner cavity sparkling with tiny quartz crystals. Commonly found in locations like Brazil, Mexico, and the United States (such as Indiana and Iowa).