Understanding Diamond Grading and the 4 C’s

Understanding Diamond Grading and the 4 C’s

Until around the 1950s, there was no globally accepted standard for describing or grading diamonds until the GIA or the Gemological Institute of America created the 4Cs: Color, Clarity, Cut and Carat Weight. Until then, there was no universal method for determining the quality of a diamond.

A diamonds Color grade is based on the lack of color ranging from colorless to dark yellow represented by the letters D through Z. See the illustration below.

After Cut, Color is generally considered the second most import characteristic when choosing a diamond. If you can afford it, nothing tops a diamond with a color of D or F, but most diamonds are sold in the near colorless G to I range. Unless the two types are placed side by side, most people cannot tell the difference.


Clarity is defined by the lack of blemishes and inclusions found on and in a diamond. Blemishes are found on the outside of a diamond and inclusions are found on the inside. Clarity grades range from Flawless to Included represented by FL to I3. See illustration below.

Some common inclusions include small internal breaks called feathers, crystals that were trapped during the diamonds formation and graining caused by an irregular atomic structure. Blemishes are mainly caused by cutting, polishing and wearing of a diamond.

It is extremely rare to find a diamond that is flawless and most diamonds sold in the jewelry industry range from the I2 to SI1 grade. Many people think clarity is the most important factory in the beauty of a diamond, but that is simply untrue. A diamond with a superior Cut and Color grade is much more important to the amount of sparkle a diamond produces.

The Cut grade is the most important factor in the beauty of a diamond. What makes a diamond beautiful is the amount of sparkle (fire, scintillation and brightness) it produces and nothing determines that more than the Cut. The Cut grades range from Excellent to Poor. See illustration below.

Three major components determine a diamonds sparkle and they are fire, scintillation and brightness. Fire describes the flashes of color emitted from a diamond. Scintillation describes the flashes of light when the diamond, the light or the observer moves. Brightness is a combination of all white light reflected from the inside and outside of the diamond.

Below is an illustration of the 5 major components of a polished diamond, the table, the crown, the girdle, the pavilion and the culet. The symmetry and proportions of these components determines the cut grade of a diamond.

Carat Weight:
The final C refers to the Carat weight of a diamond. One carat equals 200 milligrams. Diamonds under one carat are commonly divided into pointers where one pointer equals 0.001 carat. For example, a diamond with a carat weight of 0.25 carats equals 25 pointers. Or a one carat diamond equals 100 pointers.