mineral

Geode-like quartz vein in banded chalcedony

Quartz and chalcedony (SiO₂), possibly agate

AI-generated identification · may be incorrect

Gray-blue, tan, and brown concentric/banded silica with a rough vug lined by tiny quartz crystals; vitreous to waxy luster, hardness about 6.5–7 Mohs, no obvious cleavage, conchoidal fracture, and specific gravity near 2.6. The blue-gray color may reflect inclusions or mineral staining.

Identified August 20, 2026More mineral →

Explore Geode-like quartz vein in banded chalcedony in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Silica-rich groundwater deposited chalcedony and quartz in a cavity or fracture, followed by later crystal growth; such material commonly forms in volcanic rocks during the Cenozoic, though the exact age cannot be determined visually.

Uses & applications

Used as ornamental stone, cabochons, slabs, lapidary material, and mineral specimens; attractive crystal-lined cavities increase display value.

Geological facts

The cavity is a vug, and the surrounding banding is characteristic of agate or chalcedony formed by repeated changes in fluid chemistry.

Field identification & locations

Identify by its silica hardness, waxy banding, conchoidal fracture, and crystal-lined void; common sources include Brazil, Uruguay, Mexico, Madagascar, and the western United States. A scratch test with steel or glass can help distinguish it from softer rock, though testing may damage the specimen.