mineral

Quartz Geode

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale); Color: Clear to milky white; Luster: Vitreous (glassy); Crystal structure: Trigonal; Cleavage: None; Specific gravity: 2.65

Hardness: 7 (Mohs scale)
Color: Clear to milky white
Luster: Vitreous (glassy)

Identified June 20, 2026More mineral →

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Physical properties

Hardness: 7 (Mohs scale); Color: Clear to milky white; Luster: Vitreous (glassy); Crystal structure: Trigonal; Cleavage: None; Specific gravity: 2.65

Formation & geological history

Formed as hollow cavities in sedimentary or volcanic rock that are filled over time by the slow precipitation of mineral-rich water. Geological age can range from thousands to millions of years depending on the host strata.

Uses & applications

Primarily used for museum displays, home decor, geological collecting, and lapidary arts. Some smaller specimens are used in jewelry.

Geological facts

The word geode comes from the Greek word 'Geoides' meaning earth-like. Unlike a vug, which is any cavity in a rock, a geode is a specific spherical or subspherical structure.

Field identification & locations

Identify by looking for a bumpy, cauliflower-like exterior on a round rock that feels lighter than a solid rock of the same size. Commonly found in deserts (Sahara, Chihuahua) and limestone-rich areas (Midwest USA).