Exodus 28:11-12

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. 28:12 You are to put the two stones on the shoulders of the ephod, stones of memorial for the sons of Israel, and Aaron will bear their names before the Lord on his two shoulders for a memorial.

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.