Let’s Talk Diamonds: Understanding the Four C’s

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The scene plays out in jewelry stores across the country every day: a young man walks in, looking a little sheepish but determined. He’s there to buy an engagement ring. Although he tries to describe what he’s looking for, he may rely on the jeweler to walk him through the process. The conversation that follows usually begins with the basics of how one diamond differs from another. These differences are typically known as the four C’s – cut, color, clarity and carat weight.

A Uniform System

Until the mid-twentieth century, there was no agreed-upon method for comparing one diamond to another. The Gemological Institute of America (GIA) created the four C’s to solve this problem, and jewelers have been using them ever since. We believe the independent certification provided by the GIA is still the most credible certification in use today. The independent certification removes any bias in the grading and ensures that the retailer did not grade it higher than it should be in an effort to make more money or falsely lead the customer into thinking that he is getting a better deal.

According to experts at the GIA, creating the four C’s meant two important things: “Diamond quality could be communicated in a universal language, and diamond customers could now know exactly what they were about to purchase.” Let’s take a closer look.


A diamond’s cut refers to how well its facets interact with light. If a stone is cut too shallow or too deep, the light entering through the top is allowed to escape, and the diamond’s brilliance is compromised.

Depending on the stone’s initial qualities and dimensions, types of cuts can include round, radiant, princess, pear, oval, marquis, heart and emerald.


This is a slight misnomer, since diamonds are actually graded on their lack of color. Stones are graded on a scale of D to Z, with D being colorless, and then continuing with an increasing presence of color to the letter Z.

Chemical impurities or structural defects can affect a diamond’s color. Stones can be found in hues that include white, blue, yellow, black, orange, red, green, pink, purple, brown and gray.


Clarity refers to the location (and amount) of imperfections in a stone when viewed at 10x magnification. Internal imperfections are referred to as inclusions, and external imperfections are called blemishes. Diamonds are rated on a clarity scale ranging from flawless (no inclusions or blemishes visible at 10x magnification) to included (inclusions are obvious at 10x magnification and may affect transparency and brilliance).

Carat Weight

Just like it says, carat weight refers to how much a diamond weighs. According to the GIA, a metric carat is defined as 200 milligrams. Each carat is then divided into 100 points, which allows for very precise measurements.

While diamonds come in all shapes and sizes, some are considered the “magic” size – half carats, three-quarter carat, and a carat. Even though there is almost no visible difference between a one-carat diamond and another that’s only a few points lighter, the difference in price can be substantial.

Keep in mind that all four C’s play a role in the appearance of a diamond. Understanding how each of these affects a diamond’s characteristics will help you make a purchase that’s right for you.

Jeff Johnson & Co. is a full-service jeweler located in Upper Arlington, Ohio. We specialize in custom engagement rings, keepsakes for significant moments, and giving new life to family heirlooms. Our gemologists are trained by the Gemological Institute of America, and they work closely with each customer to ensure that we meet your vision and beyond. Stop by our showroom at 5025 Arlington Centre Blvd. (off Henderson Road), call 614-459-8890, orjjandcompany.com. You can also follow us on Facebook at Jeff Johnson & Co.