Sapphire
Archimandrite Nikifor’s Biblical Encyclopedia
(Exod. 28:18; Rev. 21:19)—a precious stone surpassed, in the source’s description, only by the diamond in beauty, brilliance, and hardness. Its deep azure or cornflower-blue color resembles the heavens and may underlie the imagery in Exodus 24:10 and Ezekiel 1:26 and 10:1. Sapphire was the second stone in the second row of the high priest’s breastplate of judgment and is numbered among the foundation stones of the holy city, the heavenly Jerusalem. The ancients obtained it from Ethiopia and India.