mineral

Quartz geode (druzy quartz)

Quartz, silicon dioxide (SiO₂), commonly lining a volcanic-rock cavity

AI-generated identification · may be incorrect

White to gray botryoidal and druzy quartz crystals with vitreous to sugary luster; Mohs hardness 7, trigonal crystal structure, no cleavage, conchoidal fracture, specific gravity about 2.65. The tan outer rind is likely weathered silica-rich host rock or iron staining.

Identified September 13, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater deposits quartz crystals inside gas vesicles or cavities, commonly in basaltic volcanic rocks; individual geodes may range from Paleozoic to Cenozoic in age. The specimen appears cut or naturally broken open to expose the cavity.

Uses & applications

Used as a decorative and educational specimen, crystal display, and lapidary material; generally unsuitable for construction because of its small size and irregular form.

Geological facts

Druzy quartz consists of a coating of many tiny crystals, while the rounded masses are botryoidal aggregates. Quartz can scratch ordinary glass and is unaffected by dilute hydrochloric acid.

Field identification & locations

Identify by its sparkling glassy crystals, hardness, and lack of acid fizz; test cautiously because scratching can damage the specimen. Common sources include Brazil, Uruguay, Morocco, Mexico, and the western United States.