Amethyst
Archimandrite Nikifor’s Biblical Encyclopedia
(Exod. 39:12) — one of the precious stones in the high priest’s breastplate, namely the third, in the third row; it occurs in various colors, but chiefly purple. This word occurs in the New Testament only once, namely in Revelation 21:20, where it is said that the twelfth foundation of the new Jerusalem was amethyst. The name of the stone, it is thought, derives from a word meaning “wine.” The ancient Greeks considered it an amulet, protecting against drunkenness.