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Learning Center

Physical and Optical Properties of Gemstones

Learn about gemstone color, crystallography, hardness, chemical makeup and more.
Gemstone Physical Properties

The optical properties of gems attract our eyes and can give a cut stone a unique character. However, gemstone physical properties are also important.…

Gemstone Optical Properties

Learn how gemstone optical properties, like refractive index and pleochroism, help gemologists identify gems and lapidaries choose cuts.

What are Gemstone Enhancements?

Gemstone enhancements improve the appearance and wearability of gems. Learn about the most commonly used procedures and frequently treated…

Gemstone Thermal Properties

Non-destructive tests are critical for gemologists trying to identify gems. Learn how measuring thermal properties, especially thermal inertia,…

What is Gemstone Pleochroism?

Some gems show pleochroism, two or three different colors depending on the viewing angle. Learn why this occurs and how it helps gemologists identify…

Gemstone Optics: The Basics

Accurately measuring optical properties is critical for identifying gemstones. This article covers the basic terminology and concepts of gemstone…

What is Gemstone Cleavage?

Gemstone cleavage is a break in a crystal along internal planes. Learn the science behind this and the difference between cleavage, fracture,…

What is Gemstone Luminescence?

Gemstone luminescence is a glow that occurs when certain stones are subjected to energy such as UV light. This effect can help gemologists identify…

Gemstone Color Change Phenomena

Frequently, people ask me to explain how gemstone color change works. Some stones can change color under different light sources. Although the…

Understanding Color in Gemology

The color of a mineral or gemstone is one of the primary attributes used for identification,but it is, unfortunately, one of the least diagnostic…