mineral

Polished banded agate (likely carnelian and black agate)

Chalcedony, microcrystalline quartz (SiO₂), with iron-oxide coloration

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; waxy to vitreous luster; translucent reddish-brown and opaque dark-gray bands; cryptocrystalline, with no visible cleavage and conchoidal fracture. The smooth surface indicates a polished or tumbled specimen.

Identified September 21, 2026More mineral →

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At a glance

Common name: Polished banded agate (likely carnelian and black agate)
Scientific name: Chalcedony, microcrystalline quartz (SiO₂), with iron-oxide coloration
Category: mineral
Identified: September 21, 2026
Method: Standard

AI Estimated Value

Approximately $5–$30 for a small polished piece; $30–$100+ for unusually attractive patterning, larger size, or quality jewelry-grade material.

Not an official valuation

AI estimate for general interest only — not an appraisal. Actual value depends on condition, provenance, and market demand. Verify with a professional before buying, selling, or insuring.

This identification was generated by AI and may contain errors. Verify important details before relying on them — and never use an AI result to judge whether a specimen is safe to handle. Read the full disclaimer

Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rock, depositing successive layers of chalcedony; iron oxides create red-brown tones. Individual agates commonly formed during volcanic activity from the Paleozoic to Cenozoic eras.

Uses & applications

Used for cabochons, beads, carvings, paperweights, and decorative objects; durable and inexpensive compared with many gemstones.

Geological facts

Agate is a variety of chalcedony distinguished by banding or other patterned color zones. Red-orange areas are commonly called carnelian, while dark areas may be black chalcedony or iron/manganese-rich bands.

Field identification & locations

Identify it by its glassy-waxy polish, exceptional smoothness, fine banding, and hardness; it should resist scratching by steel but be scratched by quartz. Common sources include Brazil, Uruguay, India, Madagascar, Mexico, and the United States.