mineral

Polished agate-like stone (uncertain; possibly a fossil or shell fragment)

Likely microcrystalline quartz (chalcedony), SiO₂; exact identification is limited by the image

AI-generated identification · may be incorrect

Small, smooth, cream-white specimen with a black inclusion or band and possible curved shell-like structure; likely Mohs hardness 6.5–7, vitreous to waxy luster, no obvious cleavage, and quartz microcrystals. The apparent hole and irregular curvature may indicate fossil material rather than agate.

Identified August 25, 2026More mineral →

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At a glance

Common name: Polished agate-like stone (uncertain; possibly a fossil or shell fragment)
Scientific name: Likely microcrystalline quartz (chalcedony), SiO₂; exact identification is limited by the image
Category: mineral
Identified: August 25, 2026
Method: Standard

AI Estimated Value

Typically $1–$10 if common and unidentified; $10–$50 if confirmed as an attractive agate or fossil.

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

If agate, it formed when silica-rich groundwater filled cavities in volcanic rock, commonly during the Cenozoic or older. If fossil shell, it formed from biomineralized material later replaced or coated by silica.

Uses & applications

Decorative or collectible specimen; polished agate is used in jewelry, cabochons, ornaments, and lapidary work. A small unidentified fragment has negligible industrial value.

Geological facts

The black area could be manganese-oxide staining, iron-rich material, matrix, or an organic cavity. A hardness or streak test would help distinguish chalcedony from carbonate shell or plastic.

Field identification & locations

Common agate sources include Brazil, Uruguay, Mexico, India, and the western United States; fossilized shells occur worldwide. Check translucency, quartz-like hardness, and whether a steel file scratches it.