What Makes a Diamond Sparkle?
Diamonds have great power to break up rays of light into all the colors of the rainbow and get their brilliance from three things: reflection, refraction and dispersion.
Reflection is the light that hits the diamond and is immediately bounced back up, giving it an instantaneous shine. While this glimmer is impressive, it’s only the very tip of the true radiance a diamond displays.
Only a portion of the light hitting a diamond is reflected; the rest travels through it. As the light moves through the diamond, it is scattered and fractured, creating the sparkle that diamonds are known for. This is the refraction.
In essence, diamonds are tiny, complicated prisms; the light enters through the top, and then is angled around the inside of the diamond before being aimed back towards the top and out through the surface.
This creates a rainbow effect (dispersion), and adds to the shine. Most diamonds just look like dull pieces of glass when they are taken from the ground. In order to become a sparkling jewel, a diamond must be carefully cut and polished. The stone is first shaped with a diamond cutting tool.
Many little sides, or facets, of the diamond are then polished by holding it against a spinning disk coated with diamond dust. Upon entering a diamond facet, a light ray is refracted (bent). The bent ray is reflected out as a glittering rainbow.