gem so called

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

sardius

carnelian, a precious stone.

gem

sardian (3037 being implied), i.e. (as noun) the gem so called

sardius

σάρδιον, -ον, τ [in LXX for אֹדֶם, Exo.28:17, al.; also for שֹׁהַם ;] the sardian stone, sard (of which carnelian is one variety): Rev.4:3 21:20.† (AS)