mineral

Quartz Geode

Silicon dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: White to translucent; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (trigonal); Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Hardness: 7 on Mohs scale
Color: White to translucent
Luster: Vitreous (glassy)

Identified April 11, 2026More mineral →

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Physical properties

Hardness: 7 on Mohs scale; Color: White to translucent; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (trigonal); Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Formation & geological history

Formed as secondary mineral precipitates in hollow cavities (vugs) within igneous or sedimentary rocks. Over millions of years, mineral-rich groundwater seeps into these cavities, depositing layers of crystals inward.

Uses & applications

Primarily used as decorative specimens, in gemstone collecting, and occasionally sliced for jewelry or metaphysical purposes. Industrial silicon is used in electronics and glass-making.

Geological facts

Geodes are often called 'thunder eggs' when they are solid or nearly solid. The name 'geode' comes from the Greek word 'geodes', meaning earth-like, referring to their round, drab exterior which hides an interior crystal treasure.

Field identification & locations

Identify in the field by looking for rounded, lumpy nodules that feel lighter than solid rocks of the same size. They are commonly found in arid regions, volcanic ash beds, or limestone deposits in locations like Brazil, Mexico, and the Midwestern US.