WordNet Dictionary
Webster's 1913 Dictionary\Sar"do*nyx\, n. [L., fr. Gr. ?. See {Sard}, and {Onyx}.] (Min.) A variety of onyx consisting of sard and white chalcedony in alternate layers.
Easton Bible Dictionary(Rev. 21:20), a species of the carnelian combining the sard and the onyx, having three layers of opaque spots or stripes on a transparent red basis. Like the sardine, it is a variety of the chalcedony.