gemstone

Black stone-bead bracelet, likely black onyx or agate

Probably chalcedony, microcrystalline quartz (SiO₂); the photo alone cannot confirm the bead material

AI-generated identification · may be incorrect

Polished, opaque black, glassy to waxy luster; quartz hardness 6.5–7 Mohs, no visible cleavage, trigonal crystal system. Beads may be dyed or treated, and some black beads are made from other materials.

Identified October 13, 2026More gemstone →

Explore Black stone-bead bracelet, likely black onyx or agate in the encyclopedia →

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Physical properties

Formation & geological history

If chalcedony, formed as silica-filled cavities or veins in rocks; the beads were cut and polished from geological material. The bracelet’s source and geological age cannot be determined from the image.

Uses & applications

Jewelry and collecting; black agate/onyx is also used for carvings and ornamental objects.

Geological facts

“Onyx” in jewelry commonly refers to uniformly black chalcedony and may be dyed; visual appearance alone is not enough to distinguish it from other black stones.

Field identification & locations

A scratch, hardness, or magnification test can help identify the material, but should be done cautiously to avoid damaging the beads. Chalcedony occurs worldwide, including Brazil, India, Uruguay, and the United States.