Understanding the 4 Cs of Diamonds — A Look at the International Diamond Grading System

Each diamond is as unique as the conditions that created it. But how do you know what separates a good diamond from a great one? How do you determine what the best diamond engagement ring is for your budget? 

The Gemological Institute of America developed the first set of standards for evaluating diamonds in the middle of the 20th century. Now, these standards have been adopted across the globe. Here, we break down the 4 Cs of Diamond Quality: cut, color, clarity, and carat weight.


The intense sparkling that we associate with diamonds is thanks to its brilliant cut. Here, we are not referring to the shape of the cut (pear, emerald, marquise, round, heart, etc.), but the quality, which determines how the gem will interact with light. Regardless of the shape, there are certain qualities that experts look for:

  • Brightness: reflected white light
  • Fire: scattering of white light into a rainbow of colors
  • Scintillation: how much “sparkle” a diamond has; the pattern of light and dark areas 

According to the Gemological Institute of America (GIA), diamond cuts are reviewed under magnification and are graded on a scale that determines brilliance, fire, and sparkle. Let’s take a look at how they’re graded:


When referring to the color of diamonds, what we actually are looking for is a lack of color — the closer a diamond is to being completely colorless, the higher its value. Diamond color is rated on a scale from D to Z, with D being completely colorless and Z being a light yellow color. It’s important to understand that “fancy color” diamonds (such as yellow or brown) are not rated on this scale.


Natural diamonds are made of carbon that has been exposed to intense heat and pressure inside the earth. Because of this process, sometimes there are small imperfections in the stone. Blemishes refer to markings on the outside of the gem, while inclusions refer to internal characteristics. Clarity is measured on a scale ranging from Flawless to Included:

  • Flawless (FL) – Under 10x magnification, no inclusions or blemishes are visible
  • Internally Flawless (IF) Under 10x magnification, no inclusions are visible
  • Very, Very Slightly Included (VVS1 and VVS2) – Under 10x magnification, inclusions may be slightly visible, but they are difficult to see even for a skilled grader
  • Very Slightly Included (VS1 and VS2) – Under 10x magnification, minor inclusions may be visible with some effort
  • Slightly Included (SI1 and SI2) – Under 10x magnification, inclusions are noticeable
  • Included (I1, I2, and I3) – Under 10x magnification, inclusions are obvious, and they may affect the transparency and brilliance of the stone

Carat Weight

The “C” that you might be most familiar with is carat weight, which indicates how much the diamond weighs. The value is expressed as a decimal point. While in general, larger diamonds will be more expensive, it is important to consider the other factors that determine the quality of a diamond as well.

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