4Cs Diamond Buying Guide: How to Buy a Diamond | Blue Nile
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Diamond Education

The 4Cs of Diamonds

This short tutorial explains the 4Cs of Diamonds - cut, colour, clarity, and carat weight - the most important characteristics to understand when making a diamond purchase.

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The most important of the 4Cs is cut because it has the greatest influence on a diamond's sparkle.

Learn More About Cut


The second most important of the 4Cs is colour, which refers to a diamond's lack of colour. The less colour, the higher the grade.

Learn More About Colour


Often the least important of the 4Cs because the tiny imperfections are often microscopic.

Learn More About Clarity


The term carat actually refers to the diamond's total weight and not its size.

Learn More About Carat


Each diamond shape has different attributes that affect price and quality grade.

Learn More About Shape


Unbiased diamond grading reports are offered with every Blue Nile diamond.

Learn More About Certification


As the largest online diamond retailer, Blue Nile offers the largest collection of the world's finest cut diamonds. Pre-selected for exceptional quality, the cut, colour, and clarity of our loose diamonds are evaluated based on a standardized grading scale. Also, 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.

Blue Nile Standards Chart

Price Match Guarantee

If you find a comparable GIA-graded diamond at a lower price, we'll review to match the price.

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Diamond Upgrade Program

We offer a lifetime diamond upgrade program on all GIA and AGSL-graded diamonds.

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Conflict Free Diamonds

Blue Nile diamonds are ethically sourced with a zero-tolerance policy for conflict diamonds.

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What Our Customers Chose

Visit our recently purchased rings and see the engagement rings other customers have created.