mineral

Quartz Geode

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale); Color: Colorless to white (milky); Luster: Vitreous (glassy); Crystal structure: Trigonal/Hexagonal crystals; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

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

Identified March 14, 2026More mineral →

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Physical properties

Hardness: 7 (Mohs scale); Color: Colorless to white (milky); Luster: Vitreous (glassy); Crystal structure: Trigonal/Hexagonal crystals; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed in hollow cavities (vugs) within volcanic or sedimentary rocks. Over millions of years, mineral-rich groundwater seeps into these cavities, depositing layers of silica that crystallize into quartz. They can range from millions to hundreds of millions of years old.

Uses & applications

Primarily used for decorative purposes, crystal healing/metaphysical practices, museum displays, and as entry-level specimens for amateur mineral collectors. Transparent quartz is also used in high-tech optics and electronics.

Geological facts

The word 'geode' comes from the Greek word 'geoides' meaning 'earth-like.' While they look like ordinary round stones on the outside, their hollow interiors can contain various minerals including amethyst, citrine, or calcite.

Field identification & locations

Identify in the field by looking for rounded, lumpy nodules that feel lighter than typical rocks of the same size (suggesting a hollow center). Common locations include the desert regions of the southwestern US, Brazil, and Uruguay. They are often found in areas with limestone or volcanic ash deposits.