GIA Diamonds - Look at Them First
GIA has high standards but must compromise them at some point.
Color and clarity grading diamonds has a bit of subjectivity which is why you should see the diamond you buy.
As I described in a recent post, the Gemological Institute of America is the standard bearer for independent gemological labs in the world. They created the standard grading scale most other labs, are the authority when it comes to research (both methods and aspects of gem stones), and have labs with the highest grading recognition. Few industry insiders will argue with their Diamond Grading Reports and Dossiers grades. However, do not trust GIA exclusively.
Why would I give such praise to GIA then doubt their authority within the same paragraph? My experience with GIA is largely what I described in that previous post. We send diamonds in for reports consistently and have for decades. For the most part, we can always predict a GIA grading report: take what we think the diamond should grade at and notch it down one grade. We see an VS2, and GIA sees an SI1. We grade a diamond as an H by comparing it to GIA certified H’s in our diamond lab, and they grade it as an I. We have argued for higher grade occasionally, but GIA stubbornly defends their process and does not change them.
Grading diamonds is not entirely subjective but is at least partially. There is an object difference between an I3 diamond and VVS1. Size and cut grading is objective, and GIA has tools that remove the objectivity entirely. However, that line becomes much blurrier going from an SI1 to VS2. Color is the same. What is the difference between an H and I color diamond. Very little.
This subjectivity combines with a jeweler’s incentive to cheat. A VS2 clarity diamond is worth more than an SI1, so a jeweler (or gem’s owner) will want the higher grade.
So what happens? Obviously, jeweler lobby GIA for relaxing their standards when grading only his/her gems. I have seen this first hand in the past as larger diamond dealers manipulate GIA into receiving higher grades. An I1 becomes an SI2, or J color becomes an I. GIA, after all, needs to cater to their clients, which are mostly gem dealers, and the damage is very limited.
The worry is when the manipulation becomes systemic, and there are whisperings of this occurring or at least of it occurring the past. GIA has multiple labs across the world: New York, California, Tel Aviv, etc. I can tell you first hand that the GIA lab in California does not compromise (at least to small dealers). However, labs outside the United States may be less reliable.
Here is some evidence of the compromise. Compare these four diamonds:
A lot of the diamond industry wonders how diamonds like the one pictured (#) get through as an SI2. Notice the amount of red in the clarity characteristics is significantly more in two of the reports. One diamond has a small feather and crystal while the others has multiple crystals, a cavity, needle, cloud, etc. yet received the same grade. This evidence is antidotal indeed; however, these examples are not most egregious I have seen. Clarity is easiest inconsistency to judge because of the mapping feature, but my guess is that color has been similarly compromised.
The takeaway is to see the diamond before you buy it. You will visibly notice a difference between the two diamonds mentioned here. Second, ask where your GIA diamond was certified. Feel more comfortable if your retailer says the United States.