Gemologists use several different gem classification methods. Learn how the most common systems work and what they cover as well as exceptions to the rules.
Learn About the American Gem Society & Our Mission
A Guide to Gem Classification - International Gem Society
Rocks, Gems and Minerals: A Fully Illustrated, Authoritative and Easy-to-Use Guide (A Golden Guide from St. Martin's Press): Shaffer, Paul R., Zim, Herbert S., Perlman, Raymond: 9781582381329: : Books
Opal Guide: Everything You Need To Know
Extremely Rare Queen Conch 8 x 6mm Natural Pearl
Scratch the Surface: Basic Gemology Facts for Beginners
Simon & Schuster's Guide to Gems and Precious Stones: Simon & Schuster, Lyman, Kennie: 9780671604301: : Books
Recommended Books on Gemology
サファイアの瞳”から辿る宝石と青い目の話|シマフィー
A Guide to Gem Classification - International Gem Society