Diamond (Heb. yahalôm), a gem, crystallized carbon, the most valued and brilliant of precious stones, remarkable for its hardness, the third precious stone in the second row on the breastplate of the high priest, Ex. 28:18; 39:11, and mentioned by Ezekiel, 28:13, among the precious stones of the king of Tyre. Some suppose yahalôm to be the “emerald.” Respecting shâmı̂r, which is translated “diamond” in Jer. 17:1, see under Adamant.