Each of the two onyx stones on the shoulder pieces of the high priestâ s ephod was engraved with the names of six different tribes of Israel , and each of the 12 precious stones that adorned his breastpiece was engraved with the name of one of the tribes . Each of the two onyx stones on the shoulder-pieces of the high priestâ s ephod was engraved with the names of six different tribes of Israel , and each of the 12 precious stones that adorned his breastpiece was engraved with the name of one of the tribes .