A precious, transparent, rich-red gemstone that is a variety of corundum. It is composed of aluminum oxide containing minute traces of chromium and iron oxide that impart the red color. It is very rare, slightly inferior to the diamond in hardness, and when of excellent quality and large size, it may exceed a diamond of the same size in value. Colors range from rose to the highly appraised deep bluish red often identified as “pigeon blood” red. “Ruby,” as used in the New World Translation, is translated from two Hebrew words (ʼoʹdhem; kadh·kodhʹ) that evidently both denote bright redness or extreme redness.

The first stone in the first row of gems on High Priest Aaron’s “breastpiece of judgment” was a ruby, and engraved upon it was the name of one of the 12 tribes of Israel. (Ex 28:2, 15, 17, 21; 39:10) The “covering” of the king of Tyre consisted of the ruby and other precious stones. (Eze 28:12, 13) Edom was Tyre’s “merchant” for precious rubies. Commercial Tyre eagerly traded its stores for these and other goods. (Eze 27:2, 16) When Jehovah, the husbandly owner of Zion, comforted her and described her forthcoming beauty, he said, in part: “I will make your battlements of rubies, and your gates of fiery glowing stones.”​—Isa 54:5, 6, 11, 12.