Dispersion

Refraction can also cause interesting color effects. The amount of refraction that take's place depends in good part on what the wavelength of the light is. Blue, for example, is bent more than red. This means that a ray of white light, composed of all colors, by extreme refraction can be separated into its parts and sorted out into a rainbow of colors. The phenomenon is known as dispersion. Some mineral structures cause greater dispersion than others. The phenomenon is seen almost at its best in diamond which, because of its high dispersive ability, kicks back a dazzling shower of separated color splashes or fire whenever struck by a beam of white light. Rutile and sphene lack most of the other fine gem characteristics of diamond, but they do well in matching its dispersion. Quartz and glass make poor substitutes for diamond because they have so little dispersion. Zircon is a commonly used substitute because it has the fire flashes of high dispersion and hardness and clarity, as well.