gemstone

Black-and-white agate or onyx bead necklace

Variegated chalcedony (microcrystalline SiO₂), possibly black-and-white banded agate; some black beads may be dyed chalcedony or hematite

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; translucent white to opaque glossy black, vitreous-to-waxy luster, cryptocrystalline quartz, with no visible cleavage. The spherical polished beads conceal diagnostic banding, and the image cannot confirm whether the black beads are agate, onyx, or another material.

Identified September 18, 2026More gemstone →

Explore Black-and-white agate or onyx bead necklace in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

At a glance

Common name: Black-and-white agate or onyx bead necklace
Scientific name: Variegated chalcedony (microcrystalline SiO₂), possibly black-and-white banded agate; some black beads may be dyed chalcedony or hematite
Category: gemstone
Identified: September 18, 2026
Method: Standard

AI Estimated Value

Approximately $10–$50 for a comparable finished strand; higher only if verified natural, unusually patterned, or made from premium material.

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; agate banding develops through repeated silica deposition, generally from Paleogene to Recent geological settings. The beads are human-cut and polished.

Uses & applications

Used for necklaces, ornamental beads, cabochons, carvings, and inexpensive jewelry. Typical value is decorative rather than gem-investment value.

Geological facts

Agate, onyx, and jasper are closely related silica varieties distinguished mainly by translucency, pattern, and color. Black coloration in commercial beads is frequently enhanced by dyeing or heat treatment.

Field identification & locations

Look for curved or parallel bands, waxy luster, translucency at thin edges, and quartz-like hardness; a steel file should not scratch it readily. Common sources include Brazil, Uruguay, India, Madagascar, Mexico, and Botswana.