sedimentary

Quartz Geode

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale). Color: Clear to white. Luster: Vitreous/glassy. Crystal structure: Hexagonal. Specific gravity: 2.65. Features a hollow cavity lined with drusy or macrocrystalline quartz.

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

Identified July 1, 2026More sedimentary →

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Physical properties

Hardness: 7 (Mohs scale). Color: Clear to white. Luster: Vitreous/glassy. Crystal structure: Hexagonal. Specific gravity: 2.65. Features a hollow cavity lined with drusy or macrocrystalline quartz.

Formation & geological history

Formed in sedimentary rock (like limestone or shale) where cavities created by gas bubbles or organic matter are filled over time by mineral-rich groundwater. Formed in various geological ages ranging from millions to hundreds of millions of years ago.

Uses & applications

Primarily used for decorative purposes, crystal healing, educational specimens, and as a popular entry-level item for rock collectors.

Geological facts

The word 'geode' comes from the Greek word 'Geoides' which means 'earth-like.' While they look like ordinary rocks on the outside, their hollow interiors can contain a wide variety of secondary mineral growths.

Field identification & locations

Identify in the field by looking for rounded, light-weight nodules that feel hollow. Common locations include Morocco, Mexico, and the Midwestern United States (Iowa/Illinois). Collectors should look for unbroken specimens that feel lighter than expected for their size.