gemstone

Black cabochon gemstone, likely onyx or agate

Likely chalcedony (microcrystalline quartz, SiO₂); exact identification is not possible from the photo

AI-generated identification · may be incorrect

Polished oval cabochon with a dark gray-black, glassy-to-waxy luster. Chalcedony has Mohs hardness 6.5–7 and a trigonal microcrystalline structure; the setting obscures diagnostic features.

Identified September 30, 2026More gemstone →

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At a glance

Common name: Black cabochon gemstone, likely onyx or agate
Scientific name: Likely chalcedony (microcrystalline quartz, SiO₂); exact identification is not possible from the photo
Category: gemstone
Identified: September 30, 2026
Method: Standard

AI Estimated Value

Approximately $10–$100 for a typical ring, depending on stone identity, treatment, metal, and craftsmanship.

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

Polished oval cabochon with a dark gray-black, glassy-to-waxy luster. Chalcedony has Mohs hardness 6.5–7 and a trigonal microcrystalline structure; the setting obscures diagnostic features.

Formation & geological history

If chalcedony, it formed as silica-rich fluids filled cavities or fractures and deposited microscopic quartz fibers. Such deposits occur in rocks of many ages and geological settings.

Uses & applications

Used for jewelry, carvings, and ornamental objects; this specimen is mounted as a ring stone.

Geological facts

Black onyx is a banded variety of chalcedony, though uniformly dark stones sold as onyx may be dyed or otherwise treated.

Field identification & locations

A reliable distinction among onyx, black agate, and other dark stones requires close inspection or gemological testing; look for natural banding and test hardness only on an inconspicuous loose sample.