When purchasing diamond jewelry online or at a retail store, you should receive a “Certificate of Authenticity” for each item of diamond jewelry ordered. The certificate should detail all the properties and characteristics of the diamond purchased, such as Clarity, Color, Shape, Cut, Diameter, Carat Weight, type of Metal, and the appraisal value. This certificate guarantees the purchaser that their diamond is independently and accurately rated.
Independent accredited gemological laboratories like the Gemological Institute of America (GIA) and the American Gem Society (AGS) are recognized worldwide.
The GIA are experts in certifying loose diamonds. The GIA will issue a certificate for each diamond they certify. A GIA certification is recommended for the center stones of diamond engagement rings and also stud earrings. However, a GIA certification for jewelry items such as diamond necklaces or diamond tennis bracelets will usually not be cost-effective as the GIA issue a certificate for each diamond in the jewelry item and charge a fee for each certificate. In these cases, the expense of all the certificates may end up costing more than the jewelry item itself.
American Gem Society
Another high quality diamond certified laboratory is AGS. Their standards are on the same level as GIA. AGS also grades Cut for fancy cut diamonds.