mineral

Blue-gray chalcedony geode with druzy quartz

Microcrystalline quartz (SiO₂), with quartz druse; possibly agate/chalcedony

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent blue-gray to cream, with a vitreous-to-waxy luster and sparkling drusy crystals. Quartz is trigonal and lacks cleavage, showing conchoidal fracture; the rough exterior appears weathered or matrix-coated.

Identified September 3, 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 tiny quartz crystals. Such geodes commonly formed in Cenozoic to Paleozoic volcanic flows, depending on locality.

Uses & applications

Used as a decorative specimen, lapidary material, bookend, or jewelry component; attractive blue chalcedony and druzy pieces may be polished or set in cabochons.

Geological facts

The blue color may result from microscopic inclusions or trace elements and can be enhanced by dyeing in commercial material. Druzy quartz consists of thousands of tiny crystals coating a cavity surface.

Field identification & locations

Identify by its waxy chalcedony body, silica hardness, curved fracture, and glittering quartz coating; common sources include Brazil, Uruguay, Mexico, Turkey, and the western United States. A scratch test with steel or glass can help, though it may damage the specimen.