Exodus 28:9-12

You shall take two onyx stones and engrave on them the names of the sons of Israel, six of their names on the one stone and the names of the remaining six on the other stone, according to their birth. As a jeweler engraves a signet, you shall engrave the two stones according to the names of the sons of Israel; you shall set them in filigree settings of gold. You shall put the two stones on the shoulder pieces of the ephod, as stones of memorial for the sons of Israel, and Aaron shall bear their names before the LORD on his two shoulders for a memorial.