mineral

Quartz geode

Microcrystalline and druzy quartz (SiO₂), likely chalcedony-lined

AI-generated identification · may be incorrect

Hardness 7 Mohs; pale chalcedony exterior with a cavity coated in tan to brown sparkling quartz druse. Quartz has a hexagonal crystal structure, vitreous luster, no cleavage, and specific gravity about 2.65; the brown color may reflect iron staining or inclusions.

Identified August 15, 2026More mineral →

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Physical properties

Formation & geological history

Formed when silica-rich groundwater deposited chalcedony and quartz crystals inside a gas vesicle or cavity in volcanic rock, likely over millions of years. The specimen appears cut or naturally broken open to expose the crystal-lined vug.

Uses & applications

Used as a decorative and lapidary specimen; larger, colorful geodes are popular for display and collecting, while quartz is also important in glass, electronics, abrasives, and optical applications.

Geological facts

The sparkling surface is called druzy or druse, consisting of many tiny quartz crystals. Individual crystals can often be confirmed with a steel file or glass-scratch test, though testing may damage the specimen.

Field identification & locations

Commonly found in basaltic volcanic regions and sedimentary cavities, including Brazil, Uruguay, Mexico, Morocco, and the United States. Identify it by its hollow chalcedony shell and glittering quartz lining; brown coloration is commonly iron staining.