mineral

Quartz geode slice

Microcrystalline and crystalline quartz, silicon dioxide (SiO₂)

AI-generated identification · may be incorrect

White to translucent drusy quartz lining a rounded cavity, with a dull gray-brown outer rind; vitreous luster, hexagonal crystal structure, Mohs hardness 7, no cleavage, and specific gravity about 2.65.

Identified August 25, 2026More mineral →

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Physical properties

Formation & geological history

Formed when silica-rich groundwater filled a vesicle or cavity in volcanic rock, depositing chalcedony and later quartz crystals. The exact age is unknown; similar geodes commonly form in Cenozoic volcanic rocks.

Uses & applications

Used as a decorative specimen, paperweight, and lapidary material; attractive crystal-lined pieces may be mounted or polished for display.

Geological facts

The rough outer shell is commonly chalcedony or silica-rich volcanic material, while the sparkling interior consists of quartz crystals. The specimen appears cut or broken open rather than naturally exposed.

Field identification & locations

Identify quartz by its glassy sparkle, hardness, lack of cleavage, and inability to scratch it with a steel knife easily; geodes are common in basaltic volcanic regions, especially Brazil, Uruguay, Mexico, and the U.S. Midwest.