mineral

Quartz Geode

Crystalline Silica (SiO2)

Hardness: 7.0 on Mohs scale; Color: Milky to translucent with brownish-yellow staining; Luster: Vitreous to greasy; Crystal Structure: Trigonal/Hexagonal; Cleavage: None/Conchoidal fracture; Specific Gravity: 2.65

Hardness: 7
Color: Milky to translucent with brownish-yellow staining
Luster: Vitreous to greasy

Identified June 30, 2026More mineral →

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Physical properties

Formation & geological history

Formed via hydrothermal precipitation where silica-rich fluids fill cavities in sedimentary or volcanic rocks. Over time, crystals grow inward from the cavity walls. Common in limestone or volcanic ash beds.

Uses & applications

Used primarily for geological education, home decor, metaphysical collections, and as lapidary material for jewelry cabochons.

Geological facts

Geodes are often nondescript 'lumpy' rocks on the outside, but when cracked open, they reveal a hollow cavity lined with crystals. This specific specimen shows iron oxide staining common in surface-found geodes.

Field identification & locations

Identify in the field by checking for unusually light weight for its size (indicating a hollow center) and a rounded, bumpy exterior (cauliflower-like texture). Commonly found in the American Midwest (Keokuk region) and Brazil.