gemstone

Black onyx bead necklace

Black chalcedony, a microcrystalline quartz variety (SiO₂); beads may be dyed or treated

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; glossy black, opaque, with a vitreous-to-waxy luster and no visible crystal faces. The beads are polished and paired with metal-colored spacers; the image cannot confirm the stone or metal composition.

Identified October 2, 2026More gemstone →

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Physical properties

Formation & geological history

Chalcedony forms as silica deposited in cavities, commonly in volcanic rocks; its geological age varies by deposit. Black onyx jewelry is often made from naturally dark or dyed chalcedony.

Uses & applications

Used for beads, jewelry, carvings, and ornamental objects.

Geological facts

“Onyx” conventionally refers to banded chalcedony, though uniformly black beads are commonly marketed as black onyx.

Field identification & locations

Check for natural banding and consistent color; dyed beads may show color concentration around drill holes. Chalcedony occurs worldwide, including Brazil, India, Madagascar, and the United States.