Physical and Optical Properties of Gemstones
Learn about gemstone color, crystallography, hardness, chemical makeup and more.
Jade Toughness and Care
Gemstone Optics: The Basics
Gemstone Optical Properties
What is Gemstone Cleavage?
Descriptive Crystallography for Gemologists
Gemstone Color Measurements and Specifications
Gemstone Color Change Phenomena
What are Allochromatic and Idiochromatic Gems?
Phenomenal Gems: Cat's Eyes, Star Stones, and More
Gemstone Physical Properties
What are Gemstone Enhancements?
Gemstone Thermal Properties
What is Gemstone Pleochroism?
Gemstone Magnetism: The Forgotten Property
What is a Trapiche Emerald?
What is Gemstone Luminescence?
Evaluating Gem Color: Hue, Tone, and Saturation
Understanding Color in Gemology
When you join the IGS community, you get trusted diamond & gemstone information when you need it.
Get started with the International Gem Society’s free guide to gemstone identification. Join our weekly newsletter & get a free copy of the Gem ID Checklist!