Quartz Geode

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.

Identified on: 5/2/2026

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