Sapphire

Boyd’s Bible Dictionary:

A light blue gem, next to the diamond in hardness
(Ex. 24:10). Second stone in second row of high priest’s breastplate (Ex. 28:18). A foundation stone of the holy Jerusalem (Rev. 21:19).

Concise Bible Dictionary:

Sapphire Ring
When Moses, and the elders, went up into the mount to God “there was under his feet as it were a paved work of a sapphire stone” (Ex. 24:10). In Ezekiel’s vision, above the firmament, was seen the “likeness of a throne as the appearance of a sapphire stone” (Ezek. 1:26). It was one of the stones in the breastplate, and one that garnished the foundation of the holy Jerusalem. It is symbolical of heavenly glory (Ex. 28:18; Rev. 21:19). The word occurs in {vi 13511;13521}Job 28:6,16; Song of Solomon 5:14; Isaiah 54:11; Lamentations 4:7; Ezekiel 10:1 and Ezekiel 28:13. Probably an azure or sky-blue stone. Some suppose it was the Lapis-lazuli, others identify it with the modern sapphire.
Lapis-lazuli

Jackson’s Dictionary of Scripture Proper Names:

telling out: recounting