mineral

Quartz geode (chalcedony-lined geode)

Quartz, SiO₂; commonly botryoidal chalcedony with drusy quartz crystals

AI-generated identification · may be incorrect

Hardness 7 (quartz); white to translucent cream color, vitreous to waxy luster, hexagonal crystal structure, and no cleavage. The rounded botryoidal surfaces and sparkling microcrystals are characteristic of chalcedony and drusy quartz.

Identified September 12, 2026More mineral →

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Physical properties

Formation & geological history

Formed when silica-rich groundwater filled cavities in volcanic rock, depositing chalcedony and later quartz crystals layer by layer. Such geodes commonly formed in volcanic rocks during the Cenozoic or older periods, depending on locality.

Uses & applications

Used as a decorative and collectible specimen; larger polished geodes are used in interior décor and jewelry. Quartz is also important industrially in glass, electronics, and abrasives.

Geological facts

The cavity formed around a gas bubble or other void, while changing groundwater chemistry produced the layered interior. The specimen appears to be a small, naturally weathered or broken geode.

Field identification & locations

Identify by a hollow cavity, rounded chalcedony growths, and quartz sparkle; quartz scratches glass and is not scratched by a steel knife. Common sources include Brazil, Uruguay, Mexico, Morocco, and the United States.