(sarʹdi·us).

A translucent, reddish-brown variety of the mineral chalcedony used as a gemstone. According to Pliny the Elder, it was named after the city of Sardis in Lydia, where it was first introduced to that part of the world. However, it has been suggested that the name originated with the Persian word sered, meaning “yellowish-red,” and accompanied the stone from its source in Persia. Sardius has also been called “sard,” “sardine,” and “sardoine.” Its beauty, its toughness, the ease with which it can be engraved, and the fact that it can be highly polished made it a most popular stone among artisans. The Hebrews possibly obtained their sardius stones from the Arabian Peninsula.

The sardius is referred to at Revelation 4:3, where the One seated upon his heavenly throne of splendor “is, in appearance, like . . . a precious red-colored stone [“a sardius,” ftn].” “The holy city, New Jerusalem,” is described as having a wall with foundations that “were adorned with every sort of precious stone,” the sixth being sardius.​—Re 21:2, 19, 20.