Boyd’s Bible Dictionary:
A bright green variety of beryl. The emerald (Ex. 28:18; 39:11; Ezek. 27:16; 28:13; Rev. 4:3; 21:19) is supposedly the carbuncle, a fiery garnet.
Concise Bible Dictionary:
In the O.T. the word thus translated is nophek, but it is uncertain to which of the precious stones this refers. Some think it is the carbuncle (Ex. 28:18; Ex. 39:11; Ezek. 27:16; Ezek. 28:13). In the New Testament it is σμάραγδος, which signifies “live coal,” and is supposed to refer to some stone with prismatic crystals (Rev. 4:3; Rev. 21:19).
Jackson’s Dictionary of Scripture Proper Names:
enameled