Like a fingerprint, no two diamonds are the same. It’s for this reason that, when it comes to choosing a stone, understanding what makes one diamond from another becomes so important. This holds especially true given the cost and investment required in purchasing a diamond piece, or having one custom created.
To make sense of these differences, the jewelers and clients alike rely on a universal standard: the 4Cs. Developed by the Gemological Institute of America (GIA), the 4Cs are a set of guidelines designed to help gauge the quality of a given stone. Put simply, the 4Cs—cut, color, clarity, and carat—are the universal language for evaluating a diamond’s quality and beauty.
At first glance, the 4Cs might seem technical, but each plays a role in determining the value and beauty of a diamond. In this guide, we’ll break down each of the 4Cs: Cut, Color, Clarity, and Carat. We’ll discuss what each of these attributes means, how they’re measured, and why they matter.
Cut
A diamond’s cut refers to how precisely its rough original form has been shaped and faceted. A diamond’s facets are the small, flat surfaces that are carefully arranged during the cutting process. The degree to which these facets are symmetrical, proportionate, and polished determines how light interacts with the stone. A diamond’s cut plays a tremendous role in creating the signature sparkle that diamonds are known for, that is, it’s brilliance, scintillation, and fire.
As per the GIA, a diamond’s cut is graded as follows:
- Excellent: Ideal proportions and symmetry; maximum light return and sparkle.
- Very Good: Near-ideal proportions; reflects most light well.
- Good: Slightly less brilliance; acceptable but noticeably less lively.
- Fair: Limited sparkle; light leakage through the sides or bottom.
- Poor: Dull appearance; significant light leakage and poor light performance.
A lower color or clarity can easily be overshadowed by an excellent cut. It’s widely regarded as the most critical factor in a diamond’s overall beauty.
Clarity
Clarity refers to the presence of internal inclusions and external blemishes within the diamond. These imperfections are typically natural—tiny crystals, clouds, or small surface features that formed as the diamond grew deep within the earth. However, some blemishes or surface flaws can also result from the cutting, polishing, or wear of the stone.
As per the GIA, the scale for grading diamond quality is as follows:
- Flawless (FL): No inclusions or blemishes visible under 10x magnification.
- Internally Flawless (IF): No internal inclusions; only minor surface blemishes visible under 10x magnification.
- Very Very Slightly Included (VVS1 and VVS2): Inclusions are tiny and difficult to see under 10x magnification.
- Very Slightly Included (VS1 and VS2): Inclusions are minor and difficult to detect under 10x magnification.
- Slightly Included (SI1 and SI2): Inclusions cannot be seen with the naked eye, but are easily detectable under 10x magnification.
- Included (I1, I2, I3): Inclusions are visible to the naked eye can affect the stone's durability or appearance.
Most diamonds have some inclusions, but many are so small they don’t impact the beauty or durability of the stone.
Color
Color refers to the presence or absence of color within a given stone. A diamond’s color is commonly the result of trace elements trapped within it, originating from when the stone was formed deep within the Earth.
The GIA’s scale for assessing color ranks diamonds from D (completely colorless) to Z (noticeable brown or yellow hues); going down the scale, the presence of yellow hues becomes more apparent. As a general rule of thumb, the more colorless the stone, the more valuable it is. The scale is as follows.
D–F (Colorless): These diamonds have virtually no color and are exceptionally rare. They reflect the most light, resulting in a bright, icy appearance.
G–J (Near Colorless): Slight traces of color are detectable only when compared side by side with higher grades.
K–M (Faint Color): A subtle warmth or faint yellow tint is visible, especially in larger stones. Depending on the setting, this can create a vintage or antique look.
N–R (Very Light Color): More apparent yellow or brown tones that are visible without magnification.
S–Z (Light Color): Deeper color saturation that is easily seen.
Subtle color differences can be masked by the diamond’s cut and the metal of the setting. For example, near-colorless diamonds set in yellow or rose gold can appear beautifully white to the eye, making them a great choice for those who want to balance quality with affordability.
It should be noted that there’s a class of diamonds that go beyond the traditional D to Z GIA scale. These diamonds are known as “fancy” colored diamonds, and exhibit a large range of colors, from blue, to black , to pink and brown. Fancy colored diamonds are exceedingly rare, and can be quite expensive.
Carat
Easily one of the most recognizable diamond terms, carat is often misunderstood to be a measurement of diamond size. Carat is actually a measurement of a diamond’s weight, where one carat is equivalent to 0.2 grams.
While a higher carat weight generally means a larger stone, know that this isn’t always the case. Depending on how the diamond is cut and proportioned, two diamonds of equal weight can differ in the perception of their sizes.
Which C Matters Most?
While all 4Cs play a role in a diamond’s beauty and value, cut is often considered the most important. Diamonds are renowned and loved for their hallmark sparkle, and the one attribute that influences this sparkle the most is the cut.
When a diamond is cut with care and precision, it enhances everything else—amplifying its sparkle and giving it a lively, almost electric presence. Even a diamond with minor inclusions or slight color can look extraordinary if the cut is excellent. In contrast, a diamond with perfect color and clarity will fall flat if it’s cut poorly and fails to play with the light.
It’s for the influence cut plays on a stone’s light performance that many experts recommend prioritizing cut above the other Cs, especially when shopping on a budget. Opting for a slightly lower carat weight or color grade in favor of a diamond with an excellent cut can lead to a stone that sparkles more and looks more impressive overall.
Finding the Right Balance
Ultimately, the “best” diamond is the one that feels right for you. This means finding a balance between the 4Cs that fits both your budget and style.
At Paul’s Jewelers, we understand how intimidating it can be to find the right stone. Our team of jewelers and GIA graduate gemologists stands by to guide you through your diamond journey, helping educate and enlighten you along the way.
As leaders in custom jewelry, we have relationships with diamond dealers all across the globe, meaning we can help source the perfect diamond for you, at the right price. Come and visit our showroom, and experience the expertise and white glove service that has made us the preferred jewelers of Milwaukee and beyond.