Exodus 28:9-11

28:9 “You are to take two onyx stones and engrave on them the names of the sons of Israel, 28:10 six of their names on one stone, and the six remaining names on the second stone, according to the order of their birth. 28:11 You are to engrave the two stones with the names of the sons of Israel with the work of an engraver in stone, like the engravings of a seal; you are to have them set in gold filigree settings.

Exodus 28:21

28:21 The stones are to be for the names of the sons of Israel, twelve, according to the number of their names. Each name according to the twelve tribes is to be like the engravings of a seal.