mineral

Quartz Geode

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale); Color: Clear to white crystals with gray/white chalcedony banding; Luster: Vitreous to greasy; Crystal structure: Trigonal; Cleavage: None; Specific gravity: 2.65

Hardness: 7 (Mohs scale)
Color: Clear to white crystals with gray/white chalcedony banding
Luster: Vitreous to greasy

Identified May 2, 2026More mineral →

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Physical properties

Hardness: 7 (Mohs scale); Color: Clear to white crystals with gray/white chalcedony banding; Luster: Vitreous to greasy; Crystal structure: Trigonal; Cleavage: None; Specific gravity: 2.65

Formation & geological history

Formed in cavities of volcanic or sedimentary rock through the precipitation of silica-rich groundwater. Over long geological periods, mineral layers grow inward toward the center of the cavity.

Uses & applications

Primarily used for decorative purposes, crystal collecting, metaphysical use, and teaching geology to students.

Geological facts

The word geode comes from the Greek word 'Geoides' meaning earth-like. Unlike solid rocks, geodes are hollow and often contain miniature mineral ecosystems inside.

Field identification & locations

Identify by their rounded shape and hollow sound when tapped. They feel lighter than expected for their size. Common locations include the American Midwest (Keokuk, IA), Brazil, and Morocco.