A market-wide average across qualities and sizes. Your stone's value depends on carat, color, clarity, cut, treatment, and origin.
Onyx is a striking banded variety of chalcedony, known for its rich black color often accented with white or brown bands. It has a hardness of 6.5 to 7 on the Mohs scale, making it suitable for various jewelry applications, commonly cut into cabochons or beads.
Market averages will not price your stone. GemstoneAI identifies gems and jewelry from a photo, checks authenticity and treatment signals, and gives you a real market valuation in seconds. Free to try.
Featured in National Jeweler
The middle first-read value from GemstoneAI scans of each kind of onyx jewelry. All jewelry values from real scans.
The GemstoneAI market index for onyx is $5.00 per carat as of 2026-11-09. That is a market-wide average across qualities, not a quote for a specific stone. Individual value depends on carat, color, clarity, cut, treatment, and origin.
Visual tests alone are unreliable. GemstoneAI identifies the stone from a photo, shows what else it could be, and estimates market value. It is free to try.
Gem prices move on supply, demand, and metal markets; treat any single stone as a collectible first and an asset second.