
Exodus 28:17-20
17 Then mount four rows of precious stones on it. In the first row there shall be a ruby, a topaz and a beryl; 18 in the second row a turquoise, a sapphire and an emerald;
19 in the third row a Jacynth, an agate and an amethyst;
20 in the fourth row a chrysolite, an onyx and a jasper. Mount them in gold filigree settings. NIV

Many believe that the Breastplate of Aaron is the basis for the origin of birthstones (also known as natal stones). The instructions for fabricating the Breastplate are in Exodus 28: 15-30, and call for the twelve stones of the Twelve Tribes of Israel to be set in four rows.
The Breastplate was called the "Oracle of judgment" or the "breastplate of the (oracular) decision" (favorable or unfavorable). The Breastplate had 12 stones with names of 12 tribes (by blessing). Levi's name not mentioned because this tribe couldn't own anything and they were appointed to be the priesthood. Joseph's name removed and his two sons Manasseh and Ephraim are placed by blessing.