When a diamond emerges from the earth it is a rough stone, its beauty is hidden. The cut of a diamond is the one area where man has full control. A well cut Diamond will have the magnificent fire and brilliance offering maximum sparkle and reflection of light. A poorly cut diamond, no matter how great it’s other qualities, will remain dull and lifeless.
It is important to note that cut does not necessarily refer to the shape ot the gem. It is more a reflection of the symmetry, proportioning and polish of the diamond. The cut of a diamond greatly impacts a diamond brilliance; this means if it is cut poorly, it will trap the light and therefore be less luminous. If cut well, the diamond will reflect the light around it and offer maximum brilliance.
Though it is extremely difficult to analyze, the cut has three attributes: brightness (the total light reflected from a diamond), fire (the dispersion of light into the colors of the spectrum), and scintillation (the sparkle – when a diamond moves)
Every diamond regardless of its shape gets it brilliancy and scintillation by cutting and polishing the diamond facets to allow the maximum amount of light entering through its top to be reflected and dispersed back through the top. A "well made" stone has angular cuts that allow light to go through and reflect out from the top facets. When a stone is cut too shallow or too deep the light that enters through the top will either escape through the bottom or through the diamond's side preventing the maximum sparkle and glow.
Below is a guide to diamond cut and the illustration of how light is reflected throughout the facets of different cut grades of diamonds.
An understanding of the DIAMOND SHAPE is also important when making your jewelry purchase. While the standard round brilliant cut dominates the majority of diamond jewelry, other diamond shapes known as fancy shapes or fancy cuts are quickly gaining popularity. They include the princess cut, emerald cut, cushion cut, radiant cut asscher cut, pear shape, hearts and oval cut diamond.