mineral

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Hardness: 7 on the Mohs scale; Color: Clear to milky white; Luster: Vitreous (glassy); Crystal Structure: Hexagonal/Trigonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

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

Identified March 20, 2026More mineral →

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Physical properties

Hardness: 7 on the Mohs scale; Color: Clear to milky white; Luster: Vitreous (glassy); Crystal Structure: Hexagonal/Trigonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Formation & geological history

Formed as secondary mineral precipitates from hydrothermal fluids or groundwater within cavities (vesicles) of volcanic rocks or sedimentary limestone nodules. High-quality quartz geodes can range from 50 million to over 200 million years old.

Uses & applications

Primarily used for geological education, home decor, and metaphysical collecting. Industrial-grade quartz is used in electronics for its piezoelectric properties and in glassmaking.

Geological facts

Geodes are often referred to as 'thunder eggs' in some regions. While they look like plain rocks on the outside, they contain hollow cavities lined with millions of tiny, sparkling crystals.

Field identification & locations

Identify in the field by looking for rounded, bumpy, or hollow-sounding nodules that feel lighter than solid rocks of the same size. Commonly found in desert regions of the US (Utah, Arizona), Mexico, and Brazil.