mineral

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale); Color: Transparent to translucent white/milky; Luster: Vitreous (glassy); Crystal Structure: Hexagonal/Trigonal (druzy display); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 (Mohs scale)
Color: Transparent to translucent white/milky
Luster: Vitreous (glassy)

Identified March 29, 2026More mineral →

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Physical properties

Formation & geological history

Formed when mineral-rich hydrothermal fluids seep into cavities (vesicles) in volcanic rock or sedimentary limestone. Over thousands of years, crystals grow inward from the walls of the cavity. These can range from millions to hundreds of millions of years old.

Uses & applications

Primarily used for geological education, decoration, metaphysical collecting, and lapidary work. High-purity quartz is also used in electronics and glass manufacturing.

Geological facts

Geodes are essentially 'rocks with a secret.' While the exterior looks like an ordinary, bumpy stone, the interior contains a hollow or semi-hollow cavity lined with crystals. This specific specimen is a fragment showing the transition from the outer chalcedony/rock rind to the inner crystalline quartz.

Field identification & locations

Identify in the field by looking for rounded, nodules that feel lighter than they look (if hollow) and have a cauliflower-like exterior texture. Found globally, with famous deposits in Brazil, Uruguay, and the Midwestern United States (Keokuk geodes).