mineral

Polished banded agate pebble

Agate, a variety of microcrystalline quartz (SiO₂; chalcedony)

AI-generated identification · may be incorrect

Opaque to translucent, with reddish-brown, gray, and cream bands and a waxy-to-glassy polish. Quartz hardness is about 7 Mohs; trigonal crystal structure, though crystals are microscopic; no cleavage, conchoidal fracture; specific gravity ~2.6.

Identified September 29, 2026More mineral →

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Physical properties

Formation & geological history

Silica-rich groundwater deposited successive layers of chalcedony in a cavity, commonly within volcanic rock; the specimen is polished. Agates form across many geological ages, often in ancient lava flows.

Uses & applications

Used for jewelry, carvings, ornaments, and lapidary collecting; historically also used for small tools and decorative objects.

Geological facts

Agate’s distinctive bands record changing conditions during silica deposition; colors may be natural or enhanced by treatment.

Field identification & locations

Look for curved or concentric bands and a very hard, smooth surface; common sources include Brazil, Uruguay, India, and the United States. The photo shows a small polished pebble, not enough detail to determine its exact locality.