sedimentary

Quartz Geode

Silicon Dioxide (SiO2) within a sedimentary or igneous host

Hardness: 7 (Mohs scale); Color: White/Clear crystals in a tan/brown matrix; Luster: Vitreous to waxy; Crystal structure: Trigonal/Hexagonal; Cleavage: None/Conchoidal fracture; Specific gravity: 2.65

Hardness: 7 (Mohs scale)
Color: White/Clear crystals in a tan/brown matrix
Luster: Vitreous to waxy

Identified July 12, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in hollow cavities of rocks (often volcanic or sedimentary vesicles) where silica-rich groundwater slowly precipitates quartz crystals over thousands of years. This specimen appears to be from a sedimentary environment like the Keokuk region.

Uses & applications

Primarily used as decorative specimens, for educational purposes, in crystal healing practices, and as collector items.

Geological facts

The word geode comes from the Greek word 'Geoides' meaning earth-like. Unlike a vug, which is a cavity in a rock, a geode is a separate structure that can be removed from its host rock intact.

Field identification & locations

Identify in the field by looking for rounded, lumpy, cauliflower-like rocks that feel lighter than they look. Commonly found in desert regions of the US Southwest, Morocco, Brazil, and the Midwest (Indiana, Iowa, Illinois).

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