Reputable gemological laboratories, like the GIA Laboratory, are the most consistent and dependable sources of diamond grades. The grades are recorded on diamond grading reports that list the quality factors represented by the Four Cs: clarity, color, cut, and carat weight.
Diamond grading reports—some people call them certificates, or certs—date back to the middle of the twentieth century. They’ve become an enormously important part of the modern diamond trade.
Gemological laboratories grade hundreds of thousands of diamonds a year. That much repetition makes the grades on the reports highly reliable and consistent.
Systems at most major gemological laboratories are adapted from the GIA Diamond Grading System because other labs know that the GIA system is universally accepted. Even if a grade is based on the GIA system, however, the only source of an authentic GIA diamond grade is the GIA Laboratory.
A quality report from a reputable lab allows a retailer or dealer to choose a diamond without seeing it. Imagine that a Canadian retailer in Calgary, Alberta, needs a center stone for a ring he’s designing. He contacts dealers in Toronto, New York, and other large cities to see what they have in stock.
A Toronto dealer has the diamond he’s looking for: a 1.53-ct. E-VS1 round brilliant with a cut grade of Excellent. The dealer faxes the jeweler a copy of the diamond’s grading report. The retailer likes what he sees in the report and orders the diamond sight-unseen. Transactions like this happen every day, with diamonds being constantly bought and sold on the strengths of their reports.
A report can also work the other way: You can check a diamond that’s accompanied by a quality report to make sure it matches its description. This protects you against switched stones.
