mineral

Polished agate (likely carnelian/mossy chalcedony)

Chalcedony, microcrystalline quartz (SiO₂), with iron-oxide banding and possible inclusions

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; dark gray-green to brown with a reddish-brown band, waxy to vitreous luster, cryptocrystalline structure, and no visible cleavage. The rounded shape indicates tumbling or natural water wear.

Identified August 16, 2026More mineral →

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At a glance

Common name: Polished agate (likely carnelian/mossy chalcedony)
Scientific name: Chalcedony, microcrystalline quartz (SiO₂), with iron-oxide banding and possible inclusions
Category: mineral
Identified: August 16, 2026
Method: Standard

AI Estimated Value

About $3–$20 for a small common tumbled piece; approximately $20–$75 if the pattern, polish, or provenance is unusually attractive.

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 chalcedony in successive bands; iron produces red-brown coloration. Individual bands may form over long intervals, commonly in Cenozoic volcanic terrains.

Uses & applications

Used for cabochons, beads, carvings, ornaments, and lapidary specimens; durable enough for some decorative and functional objects.

Geological facts

Agate is a variety of chalcedony defined by banding or patterned coloration. This specimen may also be sold as “black agate,” though its exact variety cannot be confirmed from the photograph alone.

Field identification & locations

Identify by its hardness, waxy luster, translucency at thin edges, and curved internal banding; it should resist scratching by a steel blade. Common sources include Brazil, Uruguay, India, Madagascar, Mexico, and the western United States.