Color change is a visible change of a gem's main hue between daylight and incandescent light.
In more detail
Labs compare daylight of 5500 K to 6500 K with incandescent light of 2700 K to 3600 K. Color-change sapphires often go from blue in daylight to purple in incandescent light. Alexandrite, a chromium-bearing chrysoberyl, also changes color. Pleochroism differs: it changes with the direction of view, not the light.
On a grading report
Color: [color] in daylight, [color] in incandescent light. Species: color-change [variety].
Related terms
- Sapphire: Sapphire is corundum of any color other than red. The word alone means a blue stone; other colors take a color word, such as yellow sapphire.
- Hue: Hue is the basic color of a gem, such as red, blue or green. A second color can modify it, as in purplish red.
- Pleochroism: Pleochroism is the property of a colored doubly refractive stone to show different colors in different directions. It happens because the stone absorbs its rays differently.
- Fancy sapphire: A fancy sapphire is a sapphire of any color other than blue, such as yellow, orange, pink, purple or green.