mineral

Quartz geode slice

Microcrystalline quartz (SiO₂), chiefly chalcedony with drusy quartz crystals

AI-generated identification · may be incorrect

Typically Mohs hardness 7, vitreous to waxy luster, translucent gray-white interior, and radiating/fine quartz crystals lining a cavity; quartz has a trigonal crystal structure and no cleavage. The tan outer rind commonly contains iron oxides and weathered host rock.

Identified August 15, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills gas vesicles or cavities in volcanic rock, depositing chalcedony and later quartz crystals in layers. Individual geodes commonly formed in Cenozoic basaltic lava, though the exact age and locality cannot be determined from the image.

Uses & applications

Used as a decorative specimen, bookend, and lapidary material; attractive drusy surfaces are also used in jewelry and ornamental objects.

Geological facts

The specimen appears cut or broken across a hollow cavity, exposing a sparkling drusy lining rather than large euhedral crystals.

Field identification & locations

Identify by the hard, glassy quartz crystals, concentric chalcedony rind, and cavity texture; common sources include Brazil, Uruguay, Mexico, Morocco, and the United States. Value depends strongly on crystal sparkle, completeness, color, and size.