Onyx

Commonly understood to mean 'black', like the gemstone of the same name which is often black in color. Also Onyx definition is 'A chalcedony that occurs in bands of different colors and is used as a gemstone, especially in cameos and intaglios'. The word onyx itself comes via the Latin of the same spelling, from a Greek root meaning "claw, fingernail" (based on the fleshtone color of banded onyx stones, which resemble fingernails).