Cut is determined by the Depth and Table percentages. Without going into the physics of exactly how this works The sparkle and fire that the diamond gives out is caused by the light that enters from the top that reflects off the facets and back out the top [see picture]. Although it has become popular to mark diamonds with their cut (ideal, premium etc..) there's more to it that I hope to share with you.

The depth/table combination most likely to sparkle the most is ideal cut. This is when the round diamond has a depth percentage of between 59% - 62.5%. and a Depth percentage of 55% - 58%. Now understandably this doesn't mean that as soon as a diamond is 62.6% it suddenly loses its fire. These are at best guidelines albeit useful ones.

To illustrate this point please see the picture on the right. It looks nice? Well it has 68.2% depth! A stone like that is far from ideal but it looks great and costs up to 30% less than ideal cut. Trust me there are great values to be had on these diamonds. Lately there have been a lot of fancy gimmicks branding ideal cut diamonds. These range from giving them fancy names like signature collection to being able to see hearts and arrows using a special hearts and arrows scope (personally I'd be more impressed if I saw the Loch Ness Monster in my stone). These are all gimmicks to get you to pay more. There's no need to pay more. All you have to look for is Depth and Table they rarely lie.

When it comes to Fancy Shapes there are considerable more variables that come into play depending on the shape. A deep stone will obviously give the stone a smaller appearance. Ideally Fancy Shape Depth Percentages should be between the mid 50s and High 60s low 70s. princesses will generally be a little deeper and trilliants will be in the 30s - 40s. The table also plays a role in the appearance. Please compare the 2 princess cuts below.