What is diamond grading?

Diamond Grading involves evaluating the qualities of an individual diamond and deciding how its qualities reflect its rarity and value.
Diamond value is based on the famous 4Cs: Cut, Clarity, Color and Carat Weight. As you can notice all the factors start by C.
The 4Cs are the four main characteristics that influence and describe the beauty of the Diamond, not only the value, and help gemologist, trading operators and retailers to compare one diamond to another.
Cut refers to a diamond’s shape, faceting style, proportions and the quality of its finish. A well-cut diamond captures the light around it and makes that light perform in a breathtaking way.
Clarity is the relative absence of clarity characteristics, divided in inclusions and blemishes.

Color relates to the amount of bodycolor in a diamond. Truly colorless diamonds are extremely rare and valuable as a very unique fancy red color diamond. Most diamonds used in jewelry stores are near colorless, with at least some trace of yellow and brown.
Carat weight is the weight of a diamond expressed in metric carats. A carat is equal to 0.200 g. 
It’s very important, talking about rarity and value of a diamond, to consider the 4Cs all together. Never take only one or two. Not always a big, heavy diamond has a higher value of a smaller one. The value of a diamond is built considering all the 4Cs as one. 
The 4Cs are clearly expressed in GIG Diamond Report, in both of the available formats: the extended Diamond Report and the compact Diamond Report. In GIG Reports there are also the reference Grading Scales, to make it easier to understand Clarity, Color and Cut grading. The better a Diamond is cut and the more it has high Clarity and Color, the better it will be able to play with the light giving birth to its maximum beauty.
In the trade is common to consider one more C. The one related to the certificate. A diamond certificate is called properly Diamond Report and it’s crucial for the trading operations. In a certain sense, it guarantees that a diamond, object of purchase, is actually of the quality expressed in the report and that therefore the negotiation is taking place on the correct economic parameters. GIG suggestion is always to ask for a Diamond Report before buying a diamond and any kind of gemstones.