mineral

Quartz geode

Quartz (SiO₂), likely a chalcedony-lined geode with drusy quartz crystals

AI-generated identification · may be incorrect

Hardness 7; white to gray, vitreous to dull luster, trigonal quartz crystals, no prominent cleavage, and specific gravity about 2.65. The hollow cavity is lined with fine sparkling crystals, while the exterior is weathered and silica-rich.

Identified August 25, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater deposits chalcedony and quartz inside a gas bubble or cavity in volcanic rock, commonly basalt. Geode formation may occur over thousands to millions of years, often during Cenozoic volcanic activity.

Uses & applications

Used as a decorative specimen, educational material, and source of quartz crystals; attractive examples are sold for home décor and collecting. It has little industrial value in this small form.

Geological facts

The specimen appears to contain an off-center internal nodule or botryoidal growth, possibly chalcedony or another quartz layer. Its crystals are likely colorless or milky rather than amethystine.

Field identification & locations

Identify geodes by their rounded, rough outer rind and hollow crystalline interior; quartz scratches glass and does not react with dilute acid. Common sources include Brazil, Uruguay, Mexico, Morocco, and the western United States.