Many bishops wear a cross or a ring with a purple stone in it. Ever wonder why?
The book of Revelation gives a symbolic description of Heaven, saying it is like a city with 12 foundations, each of which was associated with an Apostle: "And the wall of the city had twelve foundations, and on them were the twelve names of the twelve apostles of the Lamb." (Rev 21:14)
It goes on to say that "The foundations of the wall of the city were adorned with every kind of jewel." (Rev 21: 19a) The twelfth foundation was adorned with amethyst (Rev 21: 20, end).