Exodus 28:9-12

And thou shalt take two onyx stones, and grave on them the names of the children of Israel: six of their names on the one stone, and the names of the six that remain on the other stone, according to their birth. With the work of an engraver in stone, like the engravings of a signet, shalt thou engrave the two stones, according to the names of the children of Israel: thou shalt make them to be inclosed in settings of gold. And thou shalt put the two stones upon the shoulder-pieces of the ephod, to be stones of memorial for the children of Israel: and Aaron shall bear their names before Jehovah upon his two shoulders for a memorial.