Last of the gems in the high priest's breast-plate (Exodus 28:20), probably the green jasper. In Revelation 21:19 it is first of New Jerusalem's foundations. It represents watery crystalline brightness, symbol of purity: Revelation 21:11, "her light was like unto a stone most precious, even like a jasper stone, clear as crystal." "He that sat upon the throne (Revelation 4:3) was to look upon like a jasper." Ebrard thinks the diamond is meant. The common jasper has various wavy colors, somewhat transparent. The king of Tyre (Ezekiel 28:13) has the jasper with eight other of the high-priest's 12 precious stones, as type of antichrist who usurps Christ's high-priesthood combined with kingship (Zechariah 6:13).
These dictionary topics are from Fausset Bible Dictionary, 1949. Public Domain.
Fausset, Andrew R. "Entry for 'Jasper'". "Fausset Bible Dictionary".