There are several ways to define the gemstone associated with a person's birth date. The first century Jewish historian Josephus believed there was a connection between the twelve stones in Aaron's breastplate (signifying the tribes of Israel), the twelve months of the year, and the twelve signs of the zodiac.
Modern lists of birthstones have little to do with either the breastplate or the Foundation Stones of Christianity. Tastes, customs and confusing translations have distanced them from their historical origins. Ancient traditional birthstones are now society-based birthstones. The overview above contains the stones which are popular choices.
For a detailed overview of all birthstones from all different cultures, click here.