Sardonyx

Chamber's Twientieth Century Dictionary · 1908 · p. 93

sär′dō-niks, n. a variety of onyx consisting of layers of light-coloured chalcedony alternating with reddish layers of cornelian or sard: ( her. ) a tincture of sanguine colour when the blazoning is done by precious stones. [Gr. sardonyx — Sardios , Sardian, onyx , a nail.]