Boyd’s Bible Dictionary:
A colored quartz
Last stone in high priest’s breastplate, and first in New Jerusalem foundation (Ex. 28:20; Rev. 21:19).
Concise Bible Dictionary:
This is not considered to be the same as the modern jasper, which is an opaque variety of quartz of many different colors. To what gem scripture refers is not known: some suppose the diamond. In Revelation 21:11 it is described as “clear as crystal.” It had a place in the high priest’s breastplate, and was one of the stones in the covering of the symbolical king of Tyrus in Eden (Ex. 28:20; Ex. 39:13; Ezek. 28:13). He who sat on the throne in heaven, as seen by John, was “to look upon like a jasper”; it is also used in the description of the heavenly Jerusalem (Rev. 4:3: Rev. 21:11,18-19). The jasper is a symbol of the communicable glory of God (compare John 17:22).
Jackson’s Dictionary of Scripture Proper Names:
he will be made bare: he will be made prominent