But GIA does not "certify" diamonds.
GTL quality analysis reports reflect some of the factors which help to determine how a diamond is valued. A color grade, a clarity grade, and a precise weight are each stated on the report. There is, however, no cut grade.

As you look for assurances, and you have every right to expect some assurance when you make a major purchase, your best guarantee is the American Gem Society member store where you shop for your diamond AGS diamond graders are trained in the use of the GIA diamond grading scale and can use that scale appropriately should you want to make comparisons. And AGS members stand behind the value statement they issue regarding each and every diamond they sell.

In the end, remember that AGS member stores are accountable to you, the customer. You can rely on the AGS grades and weights that establish the value of the diamond you are considering. You don't need a "certificate".