Abbott-Smith Manual Greek Lexicon
σάρδιον (G4556)
2 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 .†
G. Abbott-Smith, A Manual Greek Lexicon of the New Testament (1922) — public domain