The Four Cs

An understanding of the so-called “4Cs” of diamonds is a critical starting point. The 4Cs stand for: Color, Clarity, Cut, and Carat (or weight of the diamond). Meanwhile, another “C” that is important nowadays is Certificate.

Color

The color of a diamond is vital because it decides whether a diamond sparkles brilliantly and also has a crucial role in setting its price. Diamonds that do not have any color are the most valuable because they allow the largest amount of refraction of light, which gives the diamond its sparkle.
Why is that? Because a diamond is also a prism – it breaks light down into its spectrum and reflects it back to the eye of the viewer in flashes.
Off white diamonds that contain some yellow or brown do not absorb light as well and do not allow light to reflect as well, either. Consequently, the diamond’s brilliance is much lower.

In regular, or white, diamonds, there is an almost universally agreed way of grading – by using the Gemological Institute of America’s color scale. Logically, this should start with an A for best, but in the diamond world it starts with D. A diamond with a D-grade means it has no color and therefore is very valuable because the percentage of such diamonds from global production is very low. From D, the color grade goes down the alphabet, according to the light yellow or brown color, and goes down to Z as you can see from this diagram.
The grades D, E, F are considered the very best and, therefore, command very high prices. Meanwhile, the colors S, T, U, V, W, X, Y, Z, are light yellow or brown shades.

Diamond infograph color

The best and most valuable diamonds are those in the color grade D to I. Meanwhile, grades D, E and F are also regarded as near colorless, meaning they are also relatively rare.

Diamond Cut

Let’s move on to the second C – the cut. The way a diamond is cut is also critical for a diamond because it determines the brilliance of the diamond.
This diagram illustrates how vital a perfect cut is because it allows light to enter the stone through the table (the top flat part of the diamond) and go on to the pavilion (the lower angled part) where it is completely reflected back through the table. A poor cut means that light is not reflected entirely – and for the buyer that means the stone does not have as much fire, brilliance and sparkle.

Infograph of diamond cut

Clarity

When diamond people talk about the clarity of a diamond, they are checking whether it has inclusions, or flaws, inside it. Most diamonds have flaws – they were formed when the stones were created deep underground millions of years ago. Does the diamond have inclusions? If so, it will command a lower price because its so-called clarity is reduced. Scratches, or blemishes on the exterior of a diamond also has an effect on the clarity. See the diagram below for a quick view of the nature of inclusions.
The diamond industry generally accepts that there are five levels of clarity.

IF

IF stands for Internally Flawless. The diamond does not have any flaws inside it, but may have some surface blemishes. Such diamonds are extremely rare and, consequently, are the most expensive.

VVS1-VVS2

The next gradation is VVS, or Very Very Slightly Included of which there are two grades. The diamond has tiny inclusions which are very difficult to detect without a 10x magnification by a trained gemologist.

VS1-VS2

Next down is Very Slightly Included of which there are also two grades. So small are these inclusions that they can only be seen with difficulty using 10x magnification.

SI1-SI3

This means Slightly Included, and again there are two grades. This size of inclusion can be more easily seen using 10x magnification.

I1-3

Finally, there are inclusions which are big enough to be seen using 10x magnification and even the human eye.