gemstone

Black onyx or black agate bead bracelet

Microcrystalline quartz, chiefly chalcedony (SiO₂); commonly sold as black onyx, sometimes dyed black agate

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; opaque to slightly translucent, vitreous/waxy luster, black color, conchoidal fracture, and no cleavage. Beads are polished and may be dyed or heat-treated; the gold-colored spacer is non-geological metal.

Identified August 31, 2026More gemstone →

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At a glance

Common name: Black onyx or black agate bead bracelet
Scientific name: Microcrystalline quartz, chiefly chalcedony (SiO₂); commonly sold as black onyx, sometimes dyed black agate
Category: gemstone
Identified: August 31, 2026
Method: Standard

AI Estimated Value

Approximately $5–$30 for a common bracelet; $30–$100+ if made from verified natural, high-quality black onyx with precious-metal fittings.

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

Chalcedony forms when silica-rich groundwater fills cavities and fractures, commonly in volcanic rocks, through repeated deposition. Deposits are generally Phanerozoic, with commercial material from Brazil, India, Madagascar, Uruguay, and Mexico.

Uses & applications

Used for beads, bracelets, cabochons, carvings, and ornamental objects; black onyx is also used in decorative architectural stone. This is primarily a fashion and lapidary item.

Geological facts

“Black onyx” is often a trade name for uniformly dyed chalcedony rather than naturally solid-black onyx. Natural banding may be absent or hidden by the dark treatment.

Field identification & locations

Check for subtle banding, translucency at thin edges, and glass-like conchoidal fracture; quartz should resist scratching by a steel knife but not by hardened steel or topaz. Uniform color and very low price often indicate dyed agate.