There is only one
In spite of not legally protecting its grading system, the truth is that only the GIA Gem Trade Laboratory (GIA GTL) can or actually does provide ‘GIA grades.’ I am a graduate gemmologist (GIA) and possess a set of GIA-graded master colour comparison diamonds. I believe I follow prescribed grading procedures and that I can accurately delineate the GIA grade boundaries. However, all I really provide my client is an opinion of what I believe would be the grades assigned by the GIA GTL if it were to grade the stone.
This reality is understood and clearly stated by every other major grading laboratory, a fact that is confirmed by the disclosures on the backs of their reports. Each lab states the reported grades are based on their own standards and methods in existence at the time the stone was graded. The evidence suggests the specific definitions and grade boundaries are somewhat idiosyncratic to each organization. In spite of a shared vocabulary and some apparent grade-range overlap, none of the other labs claim to provide GIA grades. They’re telling us the truth; why won’t we hear them?
We would never fault an orange for being a pathetic tangerine, and yet that is precisely what we’re doing if we belittle the grades reported from one lab for not being identical to those of a different lab. Rather than proclaiming that a grading service is ‘loose’ when grading colour or ‘strict’ on clarity, maybe we could simply recognize there are differences in grade boundaries and appearance just as the market seems to have done. Research of the wholesale diamond market suggests diamonds are typically discounted to account for differences between labs’ grading. When I appraise a diamond with a Brand-X grading report stating ‘H colour, SI-2 clarity’ and my own grading is ‘J-colour, I-1 clarity,’ more often than not, I find the wholesale cost for stones with those Brand-X grades is remarkably consistent with stones agreeing with my estimation of the GIA grades. That means the consumer got what they paid for value-wise, but not what they thought they were buying grade-wise, and they’re rarely happy about it.
Some retailers have chosen to avoid the whole issue by creating proprietary grading systems. While I support this concept for the major laboratories, I believe it simply muddies the water and ultimately creates more confusion among consumers. It’s a return to the problem GIA hoped to resolve in 1953.
When confronted with confused consumers, maybe a more elegant solution would be to begin the conversation with “Oh, I thought we were talking about diamonds graded by GIA GTL. I’d be happy to locate/provide/show you stones graded by Brand-X if that’s what you really want. They wouldn’t look the same, but they would probably cost less.” This gives the retailer an opportunity to gain credibility and trust in the newly opened eyes of the potential buyer.