Dictionary entry

σάρδιον

G. Abbott-Smith's A Manual Greek Lexicon of the New Testament

σάρδιον, -ον, τό

[in LXX for אֹדֶם, Ex 28:17, al.; also for שֹׁהַם;]

the sardian stone, sard (of which carnelian is one variety): Re 4:3 21:20.†