mineral

Quartz Geode

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale), Color: Clear/white to smoky gray crystals inside a tan/brown exterior, Luster: Vitreous (glassy) on crystals, dull on outer rind, Crystal Structure: Trigonal/Hexagonal, Cleavage: None/Conchoidal fracture.

Identified April 7, 2026More mineral →

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Physical properties

Formation & geological history

Formed in cavities (vugs) within igneous or sedimentary rocks. Soluble minerals are leached out by hydrothermal fluids or groundwater, and silica precipitates over thousands of years to create crystal linings. Usually dated to the era of the host rock.

Uses & applications

Used primarily for home decor, educational specimens, metaphysical purposes, and jewelry (as druzy or small points).

Geological facts

Geodes are often referred to as 'thunder eggs' in some regions. They appear as unremarkable rounded rocks on the outside, but hold complex crystalline structures inside.

Field identification & locations

Identify in the field by looking for rounded, lumpy stones that feel unusually light for their size. Common in desert regions such as the American Southwest, Brazil, and Morocco.