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Diamond Education

The 4Cs of Diamonds

Searching for a sparkling diamond? Selecting a diamond starts by understanding the unique characteristics of each stone. Diamonds are graded based off the 4Cs - cut, color, clarity and carat weight. The 4Cs of diamonds impact the stone’s beauty and value. Learn more about each of the diamond 4Cs below.

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Putting it All Together with Diamond Quality

As the largest online diamond retailer, we offer a vast collection of the world’s finest cut diamonds. Our diamonds are pre-selected for exceptional quality with well-graded elements of the 4Cs: cut, color, and clarity.

Each of the individual 4Cs of diamonds may interact with one another to impact a stone’s overall appearance. For example, an ideal cut diamond may appear less brilliant if its color rating is L or M. A well-cut stone may appear larger than a diamond of the same carat weight thanks to increased light reflection.

The 4Cs of our loose diamonds are evaluated based on a standardized grading scale. Each loose diamond is accompanied by a grading report from either GIA, AGSL or GemEx, independent diamond grading labs with stringent grading and certification guidelines to analyze diamond quality.

Chart displaying the Cut, Color, and Clarity grades carried by Blue Nile compared to low quality grades not carried by Blue Nile.

Fancy Shapes and the Four Cs of Diamonds

While round brilliant is the most popular diamond shape, there are many other shapes available. We offer nine different fancy-shaped diamonds that bring a personality all their own. Also known as fancy-cut stones, these diamonds are still graded by their cut, color, clarity and carat weight.

The 4Cs of diamonds can behave a little differently for fancy cuts. Cs such as clarity and carat can be more forgiving in fancy-shape diamonds. Larger tables can make these diamonds appear larger, maximizing a lower carat weight. Inclusions that are a consideration for round diamonds may be disguised or removed altogether in more specialized cuts. Fancy-shaped diamond 4Cs are also unique in terms of clarity, with different shaped stones adding their own faceting to the mix.

Colorful Diamonds

While diamond color is one of the four Cs in respect to how colorless a stone is, there are some diamonds where colorful hues are intentional and even prized. Colored diamonds are available in hues of yellow, pink, green, blue and even brown. For fancy color diamonds, color isn't about how colorless the diamond is, instead it’s about the stone’s hue, intensity, overtones and saturation. When shopping for colored diamonds, the Cs of cut, clarity and carat weight are also still important.

How to Buy a Diamond

With so many diamonds for sale, there are a lot of options to choose from. Buying a diamond doesn't have to feel like a guessing game. Learning a little about the 4Cs, diamond quality and how these influence diamond price can make the buying journey a simple one.

Every purchase is unique, but there are some core steps for buying a diamond that you can expect to navigate as you find the perfect fit.

Understanding the 4Cs of diamonds is the first step in buying a diamond. This will help you understand which qualities are most important when you start browsing stones.

Once you understand the four Cs of diamond quality, you can set your budget. We offer stunningly gorgeous diamonds for many price points.

Staying within budget is about finding the diamond with the right combination of cut, color, clarity and carat for that specific stone shape and jewelry setting. For example, if you're looking to maximize diamond cut within your budget, you may opt for a smaller carat weight stone with a high clarity rating. If carat size is your biggest focus, then you may choose a stone that’s lower in terms of clarity to maximize the carat.

We are proud to be the best jeweler for purchasing diamond jewelry online. Browse our diamonds online or visit your closest Blue Nile jewelry store to find the right diamond. For added confidence in your purchase, our diamonds include GIA, AGSL or GemEx grading reports.

You've learned about the 4Cs, set your budget, prioritized your diamond features and found a jeweler you can trust. Now, it’s time to pick the perfect diamond to fit an engagement ring, earrings or any other jewelry need. This is the fun part! Explore our impressive selection of diamonds to choose the perfect stone to add to a setting or purchase all on its own.

Diamond Buying Guide FAQs

Our Astor diamonds represent the highest-graded stones available. These diamonds feature unparalleled brilliance.

Cut is the most important characteristic of the 4Cs. Cut is responsible for the diamond’s brilliance. A symmetrical, proportionate diamond cut will bring the most sparkle.

Clarity is believed to be the least important of the four Cs. This is because many imperfections are difficult to see with the naked eye.

The higher quality a diamond is, the more expensive it will be. Each stone is unique and many less-than-perfect grades in some of the 4 Cs are difficult to see with the naked eye. For example, stones with a lower clarity score may still look eye-clean. Because of the uniqueness of diamonds, it’s possible to choose a stone with lower scoring elements of the 4Cs and still enjoy a breathtakingly beautiful diamond.

Grade Not Carried by Blue Nile Blue Nile Quality
Cut Fair and Poor Good, Very Good, Ideal, and Astor Ideal
Color L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, and Z K, J, I, H, G, F, E, and D
Clarity I1, I2, and I3 SI2, SI1, VS2, VS1, VVS2, VVS1, IF, and FL