Sardonyx
Archimandrite Nikifor’s Biblical Encyclopedia
(Rev. 21:20)—a precious stone combining the red color of sardius with the whiteness of onyx, from which it takes its name. The source says that fine sardius and sardonyx were found in Judea. Genesis 2:12 names onyx as a distinctive product of the land of Havilah. Onyx stones were used for the ephod and breastplate (Exod. 25:7; 28:9), and the names of Israel’s tribes were engraved upon two such stones (Exod. 28:9, 12). Onyx also appears in Job 28:16 and Ezekiel 28:13, and sardonyx among the stones adorning the foundations of the heavenly Jerusalem. The stone was well suited to rings, seals, and carving.