The cut of a diamond is very important to its overall beauty. Cut is so important because it determines how much sparkle, or scintillation, you get from your diamond. When we talk about cut, we aren’t talking about shape (round, square, etc), we’re talking about the way light interacts with the stone.
In an ideally cut diamond, all of the light that enters the stone is reflected from facet to facet and back out only through the top. A poorly cut stone, cut too shallow or too deep, will allow light to leak out the sides or bottom and the stone can look dull or dark. Like most things, you don’t want to use the word dull to describe your diamond.
If cut properly, the diamond will also exhibit fire and brightness. Fire is that beautiful play of colours within the sparkle of the diamond, and brightness is how much light is reflected from the diamond.
When choosing a diamond, you’ll have to choose which cut grade you want. Excellent cut will have the right proportions to reflect the most light and give you the best sparkle, fire, and brightness. You can’t go wrong with an excellent cut diamond.
Very good cut can reflect almost all of the light, but it doesn’t have the ideal proportions of excellent cut to maximize the reflection. A similar situation is true of good cut diamonds, and the proportions of this cut are even more likely to give you a darker stone. If you’re looking for a slightly lower price point but still want high quality, very good cut is the one you want.
Fair and poor cut stones just don’t have the proportions to be bright, sparkly stones. These grades are best to avoid if you can.
The GIA, Gemological Institute of America, uses this cut grading system for round brilliant diamonds. Round brilliant stones can maximize light reflection through symmetry and their polished 57-58 facets, which is what makes them sparkle so beautifully. Other diamond shapes can have amazing sparkle and brightness too, but nothing will have as much life as a round brilliant diamond.