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How to Buy a Certified Diamond

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Published July 13, 2010 | Updated August 20, 2015

Diamond jewelry should last a lifetime, and the best way to ensure that the piece you're buying is a good investment is to check that the diamonds are certified. Certified diamonds are graded by an unbiased institution, and then assigned a model number and a certificate that verifies the gem grades. Certified diamonds are always a safe purchase because you never have to question their value. Whether you are looking for a diamond engagement ring or you are investing in diamond jewelry for yourself, knowing how to buy certified diamond jewelry is an important part of the shopping process.

Buying a Certified Diamond:

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  • Certification Institute

    Choose a reputable certification institute. The most used independent laboratory in the United States is the Gemological Institute of America. The GIA invented the four C's, which is now the most widely used diamond-rating scale. The American Gem Society (AGS) is a reputable institute; the AGS uses the guidelines set by the GIA. Sometimes a jeweler might provide you with an appraisal by a GIA Gemologist (G.G.). This is just an appraisal done by a person who is a graduate of the school. If you are making an expensive diamond investment or if you want to be sure that the diamond you buy is authentic and valuable, you can arrange for an independent appraiser to verify that the diamond matches the certificate. When choosing a diamond appraiser or institute, conduct a bit of research to be sure that the organization isn't closely tied to any vendors.

  • The Process

    Learn the certification process. Diamonds are rated on four criteria: clarity, carat weight, color, and cut. These four categories are commonly referred to as "the four C's." You can learn more about the 4 C's in our diamond buying guide.

  • The Basics of the 4 C's:

    Clarity refers to the lack of flaws found within the diamond; a flawless diamond is the most desirable.

    Carat weight refers to the weight of the diamond, but this measurement may not reflect the diamond's size due to variations in cut, shape, and setting.

    Color ratings are based on the lack of color within the gem; a clear diamond is the most valuable unless you are shopping for colored "fancy diamonds"; in which case, color intensity raises the cost and value of the stone.

    Cut refers to both the shape of the diamond and the quality of the cut; a well-cut diamond has a symmetrical shape and facets that reflect a lot of light.

  • Ranking Quality

    Rank the four C's in order of importance to you. If you have an unlimited budget, you can have large, colorless, and flawless diamond jewelry. If you are looking for the best diamond jewelry on a budget, however, it is important to decide which of the four C's is the most essential to you. Large diamonds with a few imperceptible flaws make a grand statement, while small yet flawless diamonds will sparkle and shine in any simple setting. When you know what you are looking for, it is much simpler to shop for certified diamonds.