One of the 4 C’s you can control is Cut! Diamonds today can be the finest cut to date. The brilliance is far beyond what was available to us just even a few years ago. In 2006 the Gemological Institute of America began rating the quality of the diamond cut(on round brilliant cut diamonds only). Since then, diamond manufactures receive premium amounts for their finest cut diamonds. Proportion a diamond to achieve maximum brilliance, and the results are spectacular.
Unfortunately the reverse is also true. I have witnessed the worst possible proportions of diamond cutting to date. Diamonds that are cut really with the purpose to deceive the customer. Diamonds are now cut with extra fat. Rather than trim the diamond to obtain maximum brilliance, extra heavy diamonds now enter the marketplace. I really believe these must be cut for use on the internet, as I cant imagine jewelers purchasing such stones. One carat equals weight and one carat diamonds that should have been trimmed to weigh 20 to 30% less I have seen all too often. It is even possible to purchase a diamond today with a GIA cut grade of excellent, and still have a diamond with an inferior diameter. It is not a perfect rating system, just the best we have. Fancy cut diamonds lovers need to watch proportions even more, as cut grades for any cut other than round are not established.