Onyx is a banded stone, often black, used in jewellery. A black onyx ring, carved onyx, onyx beads.
Strictly it is banded in straight parallel layers, and most of what is sold as black onyx is dyed. Those layers are what made it the stone for cameos: the carver cuts through a pale band to a dark one. The Greek name means a fingernail.
1nounonyxA banded stone, often black, used in jewellery.
“She wore a black onyx ring set in silver.”
onyx is a stone.
Greek onyx means a nail or claw, from the stone's resemblance to the colour of a fingernail.
Proto-Indo-European
*h₃negʰ-
Ancient Greek
ὄνυξ — onyx
Latin
onyx
Old French
oniche
Middle English
onix
English, today
onyx
From Middle English onix (c. 1300), earlier oniche (c. 1250), from Old French oniche or onix, from Latin onyx, from Ancient Greek ὄνυξ (“onyx”). a doublet of unguis.
Etymology from Wiktionary, CC BY-SA