mineral

Quartz geode

Microcrystalline quartz and drusy quartz (SiO₂), commonly lining a chalcedony-rich cavity

AI-generated identification · may be incorrect

White to pale gray, sparkling drusy crystals lining hollow cavities; vitreous to sugary luster, Mohs hardness 7, no cleavage, conchoidal fracture, and specific gravity about 2.65. The tan outer rind is likely chalcedony or weathered volcanic host rock.

Identified August 10, 2026More mineral →

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Physical properties

Formation & geological history

Forms when gas cavities in volcanic rocks, especially basalt, are later filled by silica-rich groundwater; quartz crystals grow inward over millions of years, commonly during the Cenozoic. Exact age and locality cannot be determined from the image.

Uses & applications

Used as a decorative specimen, lapidary material, and occasionally in jewelry or home décor; attractive pieces are popular mineral collectibles.

Geological facts

A geode is defined by its hollow, crystal-lined interior rather than by a single mineral. Quartz may coat earlier chalcedony, calcite, or other minerals that have since dissolved.

Field identification & locations

Identify by the rounded hollow cavity and sharply sparkling, colorless-to-white quartz crystals; quartz should scratch glass, while calcite is softer and reacts with dilute acid. Common sources include Brazil, Uruguay, Mexico, Morocco, and the western United States.