Sapphire - Vine's Expository Dictionary of New Testament Words
Sapphire[ 1,,G4552, sappheiros ]
is mentioned in Revelation 21:19 (RV, marg., lapis lazuli") as the second of the foundations of the wall of the heavenly Jerusalem (cp. Isaiah 54:11). It was one of the stones in the high priest's breastplate, Exodus 28:18; Exodus 39:11; as an intimation of its value See Job 28:16; Ezekiel 28:13. See also Exodus 24:10; Ezekiel 1:26; Ezekiel 10:1. The "sapphire" has various shades of blue and ranks next in hardness to the diamond.