Zodiac Stones

Since gemstones come from the earth, they have historically had spiritual, metaphysical and religious significance.  They are linked to the sun, moon and stars and from the zodiac connection, other systems of gem relationships including the Twelve Tribes of Israel and the Twelve Apostles were evolved. 

You see a variation here and there, but this seems to be the most common of the systems of Zodiac Stones.   As you can see, these stones are not the same as birthstones in most cases.