Exodus 28:11-12, 21

With the work of an engraver in stone, like the engravings of a signet, you shall engrave the two stones with the names of the sons of Israel. You shall set them in settings of gold. And you shall put the two stones on the shoulders of the ephod as memorial stones for the sons of Israel. So Aaron shall bear their names before the LORD on his two shoulders as a memorial.

And the stones shall have the names of the sons of Israel, twelve according to their names, like the engravings of a signet, each one with its own name; they shall be according to the twelve tribes.