(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.

(sarʹdo·nyx).

An ornamental stone that is a variety of agate, a kind of chalcedony. It is an onyx composed of two or more layers of milk-white chalcedony and transparent red sard. However, the contrasting layer is sometimes golden or brown. The red layer showing through the white one appeared much like the color of a fingernail to the Greeks, which was probably why they applied to it the Greek word oʹnyx (meaning “fingernail”). Sardonyx is found in various places, including Palestine and Arabia.

The stone is mentioned once in the Bible, at Revelation 21:2, 19, 20, where the fifth foundation stone of “the holy city, New Jerusalem,” is a sardonyx stone.