mineral

Quartz Geode

Silicon Dioxide (SiO2)

Hardness: 7 on the Mohs scale; Color: Clear to white internal crystals with a tan/brown outer rind; Luster: Vitreous (glassy) inside, earthy outside; Crystal Structure: Hexagonal (trigonal); Cleavage: None/Conchoidal fracture; Specific Gravity: 2.65

Hardness: 7 on the Mohs scale
Color: Clear to white internal crystals with a tan/brown outer rind
Luster: Vitreous (glassy) inside, earthy outside

Identified March 16, 2026More mineral →

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Physical properties

Formation & geological history

Formed by mineral-rich water seeping into hollow cavities in volcanic or sedimentary rock. Over thousands of years, silica precipitates out of the water to form crystals. Common in ages from the Mississippian to Tertiary periods.

Uses & applications

Primary uses include decorative home decor, metaphysical/spiritual collecting, and educational tools for teaching geology. Large, high-quality geodes are used in luxury interior design.

Geological facts

The word 'geode' comes from the Greek word 'geoides' meaning 'earth-like.' While they look like ordinary rocks on the outside, they contain hollow cavities lined with crystals. Some of the largest geodes in the world can be big enough for a person to stand inside.

Field identification & locations

Identify in the field by looking for rounded, knobby stones that feel lighter than they look (indicating a hollow center). Common locations include the 'Geode State Park' in Iowa, Morocco, Brazil, and Mexico. Collectors often shake them to listen for loose internal crystals.