Diamonds are the star of many of the most lavish pieces of jewelry in the world, but what makes these small rocks shine the way they do? The short answer is that they are expertly cut and polished to maximize the diamond’s natural brilliance. The full answer is much more detailed.
Diamonds 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. This refraction and dispersion also creates natural light and dark areas in the refracted light, depending on where the light hits along the planes of the diamond.
These dark areas in the shine may seem counter-productive, but really, they are the magic needed to achieve the diamond’s trademark brilliance. The dark magnifies the intensity of the light. It’s like a candle; the flame always appears brighter in a dark room than it does in a lighted room. It all comes down to contrast; a diamond without contrast might still shine just as much, but the shine would be significantly less impressive. It would be missing the characteristic fire that diamonds need to shine.
The cut also determines just how brilliant a diamond is. If the shape is too deep or too shallow, much of the light will get lost, never bouncing back out like it’s supposed to. The angle for the refraction would let the light slip out the bottom of the diamond. To a lesser extent, the shape of the diamond also determines the shine. Today’s most popular shapes were designed to offer the best light performance. These are the cuts that enhance the brilliance of a diamond, by using the natural properties of the diamond and complex angels to not only get the best gleam, but to also assure that the actual shape of the diamond is also aesthetically pleasing.
One of the most essential elements to a diamond having the optimum amount of shine is symmetry, which is a part of how the diamond is cut and shaped. The diamond has to be even on all ends, with all of the facets cut just so. If the symmetry is off even by the slightest amount, the light won’t refract correctly.
To a lesser extent, the clarity of the diamond also affects the shine. Blemishes on the surface of the diamond limit the amount of light that can enter the diamond. Inclusions prevent the light from moving freely within the gem. These imperfections are like stop signs and speed bumps; they affect how the light travels. Fewer imperfections mean a more brilliant diamond, as there is nothing (or nearly nothing) to detract from the shine and sparkle.
After the diamond is painstakingly cut and shaped to perfectly bounce light, the final step in its completion is to carefully polish it to its final level of shine. Polishing has a lasting affect on the diamond’s brilliance. Any residual roughness or exterior blemishes are very gently eroded away. In this way, diamonds are like almost anything else; a thorough polish can really bring out the brilliance.
It’s not easy to get a diamond to sparkle and shine in exactly the right way; trained professionals need to know just how to cut and polish each stone to get the best results. You can see the results of this effort every time you notice the way a diamond casts a beautiful display of light and color as it is moved this way or that. This scintillation, or the intense array of light and colors, is a large part of what makes diamonds such a valuable and cherished gemstone.