Cardinal gem explained

Cardinal gems are gemstones which have traditionally been considered precious above all others. The classification of the cardinal gems dates back to antiquity, and was largely determined by ceremonial or religious use as well as rarity.^[1] The term has largely fallen out of use.

The five traditional cardinal gems are:

amethyst (purple) – Rare and precious in the Old World until large deposits were found in Brazil.
diamond (transparent)
emerald (green)
ruby (red)
sapphire (blue)

Notes and References

Book: The Illustrated Bead Bible: Terms, Tips & Techniques . Geary . T.F. . Whalen . D. . 2008 . Sterling . 978-1-4027-2353-7 . 69 . 19 July 2015 . 16 January 2021 . https://web.archive.org/web/20210116113404/https://books.google.com/books?id=5abGjJ54mSoC&pg=PA69 . live . en.