mineral

Quartz Geode

Crystalline Silicon Dioxide (SiO2) in a Geodic structure

Hardness: 7 (Mohs scale); Color: Transparent to white/translucent inner crystals with a tan or brown outer crust; Luster: Vitreous (glassy) inner crystals, dull/earthy exterior; Structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 (Mohs scale)
Luster: Vitreous (glassy) inner crystals, dull/earthy exterior

Identified March 16, 2026More mineral →

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Physical properties

Formation & geological history

Formed when minerals precipitate from hydrothermal fluids or groundwater into hollow cavities within volcanic or sedimentary rocks. Over thousands of years, layers of crystals grow inward from the cavity walls.

Uses & applications

Primarily used for decorative purposes, crystal healing, geological collections, and education. Large, high-quality geodes can be used in interior design.

Geological facts

The word 'geode' comes from the Greek 'geoides,' meaning 'earth-like.' While they look like ordinary rocks on the outside, their hollow center is lined with beautiful crystal growth. Small specimens like this one are often referred to as 'rattlers' if a piece of crystal has broken off inside.

Field identification & locations

Identified by a round or egg-like exterior shape with a lighter weight than solid stone. In the field, look for nodules in limestone or volcanic ash beds. Common locations include Morocco, Brazil, Mexico, and the U.S. (Iowa/Utah).

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