mineral

Quartz geode

Crystalline quartz, silicon dioxide (SiO₂), lining a volcanic geode

AI-generated identification · may be incorrect

Hardness 7 Mohs; colorless to white, vitreous luster, transparent-to-translucent crystals, typically hexagonal/prismatic though coatings obscure form; no cleavage, conchoidal fracture, specific gravity about 2.65. The rough outer shell appears pale chalcedony or quartz matrix.

Identified August 11, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater deposits quartz crystals inside cavities in volcanic rock, commonly basalt; geodes may range from Cenozoic to much older depending on host rock. The specimen is likely cut or broken open to expose the crystal-lined cavity.

Uses & applications

Used for mineral collecting, décor, and lapidary work; clear, well-formed crystals can be used in jewelry, though this specimen is primarily ornamental. Common examples have modest commercial value.

Geological facts

Quartz is one of Earth’s most abundant minerals and is piezoelectric, producing an electrical potential when mechanically stressed. Crystal size and sparkle increase collector appeal.

Field identification & locations

Identify by glassy luster, hardness, lack of cleavage, and crystals lining a hollow cavity; common sources include Brazil, Uruguay, Mexico, Morocco, and the United States. Avoid confusing it with calcite, which is softer and cleaves readily.