mineral

Quartz Geode

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Clear to white/milky crystals; Luster: Vitreous (glassy); Crystal structure: Hexagonal (trigonal); Cleavage: None/Conchoidal fracture; Specific gravity: 2.65.

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

Identified March 14, 2026More mineral →

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Physical properties

Hardness: 7 on Mohs scale; Color: Clear to white/milky crystals; Luster: Vitreous (glassy); Crystal structure: Hexagonal (trigonal); Cleavage: None/Conchoidal fracture; Specific gravity: 2.65.

Formation & geological history

Formed as hollow cavities in volcanic (igneous) or sedimentary rocks are filled by mineral-rich hydrothermal fluids over millions of years. This process typically occurs in the Cenozoic era or older, depending on the host rock.

Uses & applications

Primary uses include decorative home decor, metaphysical/healing practices, and as collector specimens. Large quantities may be used in education or as gifts.

Geological facts

Geodes are often called 'thunder eggs' when they are solid or filled with agate. Some famous geode-producing regions include the Keokuk region in the US and the Rio Grande do Sul in Brazil. The name 'geode' comes from the Greek word 'Geoides' meaning 'earth-like'.

Field identification & locations

Identify in the field by looking for rounded, lumpy, or cauliflower-shaped rocks that feel lighter than they look (indicating a hollow center). Common locations include Iowa (Keokuk), Mexico, Brazil, and Morocco. Use a rock hammer to crack open or a wet saw for a clean cut.