How Are Diamonds Graded?

October 25th, 2019 by

How Are Diamonds Graded?

Diamonds have long occupied a space in our collective consciousness as a symbol of love and affection. People who are extremely close to each other typically exchange jewelry adorned with these fantastic gemstones to express the level of care they have for one another. While diamonds, in general, are valuable, how valuable an individual diamond is contingent on many different attributes. To determine this, diamonds are graded on four different attributes, and then certified by one of several certifying laboratories. For instance, GIA diamonds are diamonds that are certified by the Gemological Institute of America.

For those curious about the four attributes and what exactly they mean, read on:


The cut of a diamond refers to how it’s refined and polished by a jeweler. Diamonds are known for their brilliance, which is directly related to their ability to reflect light. The cut of stone requires precise knowledge of the geometry required to make a stone shine as brilliantly as possible regardless of how the light hits it. A poorly cut gemstone won’t reflect light very well and will end up looking rough to the average person. On the other hand, a well-cut gemstone will have a stunning luster at any angle and look worthy of being put into a royal crown. Cut can be difficult to grade, but typically, certification organizations look at how much light is reflected from the diamond, how well it scatters light into different colors, as well as the amount of sparkle (scintillation) typical of the stone.


A diamond in its purest form will have no discernable hue and be as clear as water. These types of diamonds are the most valuable. Diamonds are examined under specialized lights to see just how pure or impure their molecular structure is. The colors given off by the stone is then rated on a D to Z scale, with D being purest and Z being the least pure.


The formation of diamonds requires immense amounts of pressure being applied to carbon. As few things in nature are done perfectly, some diamonds have blemishes of varying sizes and shapes throughout their body due to uneven pressure during the diamond’s formation. These blemishes affect the overall clarity of the diamond and make them less brilliant overall.

Carat Weight

Carats refer to the overall weight of a diamond, with 200 milligrams being a single “carat.” A 0.75-carat diamond weighs approximately 150 milligrams. When the other 3 C’s are identical, a diamond with a higher value in carat weight will typically command a higher price. However, it isn’t uncommon to find some high-carat diamonds that sell for a lower price than less bulky diamonds because the smaller diamond has much better color, clarity, and cut.


All four C’s (color, clarity, carat, cut) work together to make the overall value of a diamond. Deficiencies in one can be made up by the others. At the same time, a large deficiency can mean that no matter how excellent the diamond is in the other 3 C’s, it just can’t ever be as valuable as a diamond without blemish. Using these attributes, certification organizations give a diamond unbiased and objective measures of beauty, which is standardized from jeweler to jeweler.