mineral

Quartz Geode

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale); Color: Clear to white; Luster: Vitreous to greasy; Crystal Structure: Trigonal/Hexagonal; Cleavage: None/Conchoidal fracture; Specific Gravity: 2.65

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

Identified June 29, 2026More mineral →

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Physical properties

Hardness: 7 (Mohs scale); Color: Clear to white; Luster: Vitreous to greasy; Crystal Structure: Trigonal/Hexagonal; Cleavage: None/Conchoidal fracture; Specific Gravity: 2.65

Formation & geological history

Geodes form when mineral-rich water seeps into hollow cavities in volcanic or sedimentary rocks. Over millions of years, the minerals precipitate out and form crystals lining the interior walls.

Uses & applications

Primarily used as decorative display pieces, for geological education, lapidary art, and as a popular item for metaphysical and crystal collecting communities.

Geological facts

Geodes are often referred to as 'thunder eggs' when they are solid rather than hollow. The largest geodes ever found can weigh several tons and be large enough for a person to stand inside.

Field identification & locations

Identify in the field by looking for rounded, bumpy, potato-like nodules that feel unusually light for their size. They are commonly found in desert regions of the southwestern US, Brazil, and Uruguay.