S'ARDONYX, n. [L. sardonyches, from Gr. from Sardis, a city of Asia Minor, and a nail; so named, according to Pliny, from the resemblance of its color to the flesh under the nail.]A silicious stone or gem, nearly allied to carnelian. Its color is a reddish yellow, or nearly orange. We are informed that the yellow or orange colored agate, with an undulating surface, is now often called sardonyx.