mineral

Polished dendritic agate/chalcedony pebble

Microcrystalline quartz (SiO₂), likely agate with dark iron/manganese dendrites or inclusions

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; gray, black, brown, and cream coloration with waxy-to-glassy luster and translucent edges. Cryptocrystalline quartz has no visible cleavage and conchoidal fracture; specific gravity is about 2.6.

Identified September 10, 2026More mineral →

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Physical properties

Formation & geological history

Silica-rich groundwater filled cavities in volcanic rock, forming layered chalcedony and later mineral inclusions over millions of years. The specimen is likely naturally rounded and then polished or water-worn.

Uses & applications

Used for cabochons, beads, ornaments, lapidary pieces, and collector specimens; not generally used as a construction stone because of its small size.

Geological facts

The branching dark patterns may be dendrites—mineral growths that resemble plant forms but are not fossils. Agate’s banding and translucency distinguish it from ordinary jasper.

Field identification & locations

Identify by testing for quartz-level hardness, conchoidal fracture, waxy luster, and translucent chalcedony; common sources include volcanic terrains and gravel beaches or riverbeds worldwide. Avoid destructive testing if polished.