Quartz Geode

Physical Properties

Hardness: 7 on Mohs scale; Color: Colorless to white/opaque; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (trigonal); Cleavage: None/Conchoidal fracture; Specific Gravity: 2.65

Formation & Geological History

Formed when gas bubbles or cavities in volcanic or sedimentary rocks are filled by mineral-rich hydrothermal fluids. Over time, crystals grow inward toward the center of the cavity.

Uses & Applications

Used primarily as decorative display specimens, for collecting, metaphysical uses, and occasionally as a source for high-purity quartz in specialty industrial applications.

Geological Facts

Geodes are essentially 'rock bubble' fossils. While they appear like ordinary stones on the outside, they contain hollow cavities lined with crystals. Some of the largest geodes can be big enough for a person to stand inside.

Field Identification & Locations

Identify by looking for rounded, bumpy nodules that feel lighter than they look (indicating a hollow center). To find them in the field, look in areas with limestone or volcanic ash deposits. Common locations include the American Midwest and Brazil.

Identified on: 4/20/2026

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