Step 2: Advanced Gemology

Lesson 3

Frequently, people ask me to explain how gemstone color change works. Some stones can change color under different light sources. Although the answer is pretty complex, a few diagrams can really help.

To understand how this phenomenon works, you need to learn about light and how gems get their coloration.

White Light and Colors

We know that sunlight or white light contains all colors. Pass a sunbeam through a prism and you’ll see a rainbow on a nearby wall. You can also consider light as energy. Visible light is closely associated with infrared, which heats us, and ultraviolet, which tans our skin.

Gemologists, as well as other scientists, use a spectroscope to separate light into it’s different components. If you were to look at the sun through a spectroscope, you’d see something like the image below. Each color is a slightly different wavelength of light. Thus, scientists can describe individual colors by their wavelengths or frequencies.

gemstone color change - spectroscope

The Source of Gemstone Color

Most of us understand how paints work. If you want a custom color for your house, a salesperson adds the right amount of pigments to white to give you the…