One of my customers had this question.  What were the stones in the biblical breastplate worn by the high priest during the time of Moses?  There were twelve stone to represent twelve tribes.  Each stone had the name of the tribe inscribed on it:
Tribe       Stone    Colour
Judas       Sardius   red
Issachar     Topaz     pale green
Zebulon
    Carbuncle  deep red
Reuben    Emerald   green
Simeon    Sapphire   deep blue
Gad       Diamond   clear
Ephraim    Ligure     dull red
Manasseh   Agate     gray
Benjamin   Amethyst   purple
Dan       Beryl     bluish green
Asher     Onyx     bluish white
Naphtali    Jasper    green