mineral

Quartz geode

Microcrystalline quartz (chalcedony) shell lined with drusy quartz, SiO₂

AI-generated identification · may be incorrect

White to translucent sparkling quartz crystals coat a hollow cavity within a tan, rough chalcedony shell. Quartz is Mohs hardness 7, vitreous luster, trigonal crystal structure, no cleavage, and specific gravity about 2.65; the specimen may also contain minor calcite or iron staining.

Identified September 13, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills gas cavities or vesicles in volcanic rocks, depositing chalcedony and later quartz crystals inward. Individual geodes commonly formed in volcanic terrains during the Cenozoic or older basaltic eruptions, though the exact age cannot be determined from the image.

Uses & applications

Used as a decorative specimen, display stone, and lapidary material; attractive examples are collected rather than used structurally.

Geological facts

The sparkling coating is called drusy quartz, consisting of many tiny crystals. Quartz geodes commonly form concentric layers, with crystals growing toward the cavity center.

Field identification & locations

Identify it by its hollow rounded form, fibrous-looking chalcedony rind, glassy crystal sparkle, and quartz hardness; quartz will scratch glass, though testing can damage the specimen. Common sources include Brazil, Uruguay, Mexico, Morocco, and the United States.