Heb. nophek (Ex. 28:18; 39:11); i.e., the "glowing stone",
probably the carbuncle, a precious stone in the breastplate of
the high priest. It is mentioned (Rev. 21:19) as one of the
foundations of the New Jerusalem. The name given to this stone
in the New Testament Greek is smaragdos, which means "live
coal." Bibliography Information Easton, Matthew George. M.A., D.D., "Biblical Meaning for 'Emerald' Eastons Bible Dictionary". bible-history.com - Eastons; 1897.