Onyx owes its name to one of the more unexpected comparisons in gemological history: the ancient Greeks named the stone after a fingernail. Greek onyx (ὄνυξ) means fingernail or claw, and the name was applied to the banded chalcedony stone because its translucent, layered appearance — with alternating bands of color — resembled the layered structure visible in a human fingernail held up to the light.
The PIE root *h₃nogʰ- (nail, claw) produced cognates across the Indo-European family: Latin unguis (nail, claw — giving English ungulate, an animal with hooves), Old English nægel (nail — giving modern English nail in both the finger and fastener senses), German Nagel (nail), and Sanskrit nakha (nail, claw). The connection between fingernails and metal nails reflects the shared concept of a hard, pointed, protective covering.
Greek mythology provided an origin story for onyx. According to one version, the mischievous Cupid used an arrowhead to trim Venus's divine fingernails while she slept on the banks of the Indus River. The clippings fell into the water, and because no part of a divine body can truly perish, the Fates transformed them into stone — onyx. The story explains both the stone
Onyx has been used in jewelry, carving, and decoration since antiquity. The Romans were particularly skilled at carving cameos from onyx, exploiting the alternating dark and light bands to create relief images — the dark layer forming the background and the lighter layer the raised figure. The Portland Vase, one of the most famous objects from Roman antiquity, is made from cameo glass that imitates the layered effect of carved onyx.
In modern usage, onyx most commonly refers to black onyx — pure black chalcedony, usually dyed or heat-treated to achieve uniform color. True banded onyx, with its natural alternating layers, is rarer and more valued. Onyx marble — actually a form of calcite rather than true onyx — is used in architecture and decorative objects, valued for its translucency when cut thin.
The word has entered modern branding and technology: onyx appears as a name for everything from software platforms to luxury products, its associations of darkness, elegance, and mineral permanence making it commercially attractive.