(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.
Easton’s Bible Dictionary
Sardonyx
Easton’s Bible Dictionary (1897), public domain. Text via Theographic Bible Metadata, CC BY-SA 4.0.