Color-change sapphires are rare gems. Their basic color typically ranges from blue to violet. Under incandescent light, they can appear violetish purple to reddish purple. This phenomenon is caused by trace element impurities in a gem’s atomic structure, which cause it to absorb certain wavelengths of light. Because the wavelength mix varies depending on the light source, the sapphire’s color changes when it’s viewed in different types of light. The strength of the color change is described by g