mineral

Quartz Geode

Crystalline Quartz (Silicon Dioxide, SiO2)

Hardness: 7 on Mohs scale; Color: Clear to white; Luster: Vitreous (glassy); Crystal structure: Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

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

Identified March 1, 2026More mineral →

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Physical properties

Hardness: 7 on Mohs scale; Color: Clear to white; Luster: Vitreous (glassy); Crystal structure: Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed as secondary precipitates in hollow cavities within volcanic rocks or sedimentary limestone. Mineral-rich groundwater seeps into these cavities over millions of years, allowing crystals to grow inward. These often date back to the Cretaceous or Paleogene periods.

Uses & applications

Primary use is for decoration, metaphysical collecting, and geological education. High-purity quartz is used in the electronics and glass industries.

Geological facts

Geodes are essentially 'inside-out' rocks; their bumpy, ordinary exterior hides a hollow interior filled with crystals. The word 'geode' comes from the Greek word 'geoides' meaning earth-like.

Field identification & locations

Identify in the field by looking for rounded, cauliflower-like exterior nodules that feel lighter than they look (indicating hollowness). Major locations include the Keokuk region (USA), Brazil, and Morocco.

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