Diamond size is not everything you have been led to believe. While having a large diamond is something that is usually high on the shopping list, it is one of the least important characteristics in a stones beauty. It is always better to have a smaller diamond of better cut quality than just purely a larger diamond.
Diamond Size Technical Stuff
The carat weight of a diamond which is measured in carats refers more to the weight of the stone than just the diameter. One carat can also be expressed as 0.2 of a gram and should have an optimal diameter of 6.5mm. As a diamond increases in weight it also increases in volume in every direction. So some of an increase or decrease in diamond weight will be in the diameter and some will be in the depth. If the stone is poorly cut, it will have more of the weight in the depth, be deeper and therefore have a smaller diameter. Ultimately this stone will have less brilliance as light is lost out through the back of the stone.
Diamonds are not priced like the tax system, where every dollar over a certain amount is charged at a higher rate. With diamonds, once you hit certain key points like the 1ct mark there is a bigger than expected jump, as the whole weight of the stone is charged at the higher rate.
Why is this great to know ? If you drop in just under one of these price barriers, the price could be significantly less, even though the difference in the diameter is only a few tenths of a millimeter smaller. Which leaves either more money in your pocket, or more money that you can use to put into the cut or colour (the things you can see with your eyes). The difference in size between a 0.90ct and a 1.00 carat is 0.3mm, but the difference could be $1500 – $2000.