At Prospect Jewelers we generally carry gems certified by the Gemological Institute of America (GIA) and the American Gem Society Laboratories (AGS). We have found these two independent gem labs to be the most consistent in there grading practices. We do not take the Gem credentials provided by of any grading organization without scrutiny and verification in house. We are not opposed to working with no certified gems and often time we can find the great value gems taken in on trade or purchased over the counter. We will always examine each gem to be certain you are completely satisfied with the quality gem you purchase. We will never recommend the purchase of any diamond we would not purchase for ourselves. Guaranteed.