The information on this page is provided by GIA as a nonprofit service. Though some jewelers will sell diamonds with simply a sales certificate, most diamonds over one carat are sold accompanied by diamond grading certificates from gemological laboratories. The most widely used laboratory in the United States is the Gemological Institute of America's Gem Trade Laboratory. Few things in nature are absolutely perfect. This is as true of diamonds as anything else.
Diamonds have internal features, called inclusions, and surface irregularities, called blemishes.
Together, they're called clarity characteristics. A clarity grade is determined by the relative absence of clarity characteristics. Blemishes include scratches and nicks on a diamond's surface. Sometimes, tiny diamond or other mineral crystals are trapped inside a diamond when it forms. Depending on where they're located, they might still be there after the stone has been cut and polished.