mineral

Quartz Geode

Quartz (SiO2) within a geode structure

Hardness: 7 (Mohs scale); Color: Clear to white internal crystals with a rough, brown/tan outer rind; Luster: Vitreous (glassy) inside, dull outside; Crystal Structure: Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 (Mohs scale)
Luster: Vitreous (glassy) inside, dull outside

Identified June 19, 2026More mineral →

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Physical properties

Formation & geological history

Formed in hollow cavities of volcanic or sedimentary rocks. Over millions of years, silica-rich groundwater seeps into these cavities, depositing crystals on the inner walls. Often found in basaltic lavas or limestones.

Uses & applications

Primarily used for decorative purposes, collecting, educational specimens, and metaphysical practices. Sometimes cut and polished for jewelry components.

Geological facts

Geodes are often referred to as 'thunder eggs' when they are completely filled with minerals. They act as geological time capsules, preserving the chemical environment of the earth from the moment they began to form.

Field identification & locations

Identify in the field by looking for rounded, bumpy, potato-like rocks that feel lighter than they look (indicating a hollow center). Common in desert regions of the SW USA, Mexico, and Brazil. Always check for a hollow sound when tapped gently.