Print full article

Making the grade: Tips to ensure your lab is up to snuff

Inconsistent grading

We’re all aware of the different grading standards between labs, but what else may be adding to the confusion? I’ve seen incidents where a dealer may fail to remove markings on diamond job bags when the stone is submitted to a lab. Depending on the laboratory’s procedures, the label on the bag may be visible to the grader, swaying his or her decision. The same may occur when the diamond bears a laser inscription from a competing lab. Appraisers have reported cases where this has resulted in a matching grade by the second lab, but also incidents where the inscription was completely ignored, revealing the problem of inconsistent grading standards. In addition, sometimes the laser inscription is cited in the second lab’s grading report and sometimes it isn’t.

Difference of opinion or deception?

Recently, I graded a 1.01-carat princess-cut diamond with a small corner chip visible beneath the prong setting. The chip was not represented in the diamond plot or the report, and my measurement of the diamond’s length and width was smaller than what was indicated. Also, the report stated there was a laser inscription on the girdle, although I was unable to locate it on the diamond. I surmised the diamond had been re-polished to remove most of the chip after the lab report was issued. It appeared they were hoping the setting would cover the chip, which meant they could retain more diamond weight by not polishing it out altogether. This was a brand new, custom-made engagement ring! With most of the chip polished out and the subsequent difference in measurements, the diamond probably weighed less than one carat, thus reducing its value. After discussing the discrepancies with the client, I was asked to issue a damage report instead of an appraisal.

Don’t pre-judge the lab grading report

A diamond's setting can affect its colour grade, particularly if it's yellow gold. As such, ASA's tolerance for grading diamonds mounted in white metal is ± two grades, while grading a loose stone is ± one grade.
A diamond’s setting can affect its colour grade, particularly if it’s yellow gold. As such, ASA’s tolerance for grading diamonds mounted in white metal is ± two grades, while grading a loose stone is ± one grade.

Don’t you love when clients retain all their reports and documents? Last year, I graded a large diamond rivière necklace. Each stone was accompanied by either a GIA or EGL USA report, which had been prepared 25 years ago. I was surprised to find the grading standards between the two labs were much closer back then than they are today. I’ve seen this happen repeatedly with single-stone items, but it was interesting to see it consistently on a multiple-stone piece. This reminded me that appraisal dates can matter and to keep an open mind when presented with a lab report.

We’ve all seen the news coverage. It’s hard to pick up an industry publication that doesn’t analyze differences in grading between labs, lawsuits between vendor and consumer, and Martin Rapaport’s efforts to protect the industry’s reputation. At the end of the day, however, we must avoid the hype and provide appraisal services in the most professional, ethical, and impartial manner.

Gina5C0A0497Ret2Gina D’Onofrio has provided gemmological and jewellery appraisal services since 1992. She is an accredited senior appraiser, master gemmologist appraiser (American Society of Appraisers) and certified senior member of National Association of Jewelry Appraisers (NAJA). D’Onofrio is co-instructor for the American Society of Appraiser’s GJ-202 appraisal report writing for insurance coverage class. She may be contacted via e-mail at

Leave a Comment


Your email address will not be published. Required fields are marked *