Hey guys.. I am a certified HRD diamond grader and happened to be a BTB as well, here are some of my opinions about the different laboratories:
I can only make detailed comparison with HRD and GIA as I am a certified HRD diamond grader, but I'll try to sum up the rest of the labs as well.
GIA:
1. GIA tend to sound more reputable because of it's number of laboratories around the world thus they certify more diamonds a day compared to other labs.
GIA, in my opinion, grading is okay but they differ slightly beacause of they have multiple master stones. (basically, diamonds are compared to master stones, like checking answers in a test)
Therefore I feel that GIA colour grading is a little off. Having said that, they are NOT noticeable to naked eyes. My experience with both labs teaches me, that in the very high colours (D-E-F), HRD is generally more strict than GIA.
2. GIA has fanciful names which makes them sound good. Don't get me wrong, its nothing bad, it's just that different labs has different number categories and names to describe their stones.
Eg 1: Assuming a Fancy Yellow diamond, with the exact same specs on a HRD cert could be "very yellow", but on a GIA it's "vivid yellow", and of course a "vivid" sounds more expensive. That's why many of the wholesalers go to GIA to certify their diamonds.
Eg 2: Same exact diamond could be cut graded "Very Good" whereas for GIA it could be "Excellent". and of course "excellent" sounds better, again many of the wholesalers go to GIA to certify their diamonds. It's not that HRD under grades them, it's because their naming system is not as good as GIA. The latest I've heard is that HRD is working towards a better naming system.
3. Other boring differences which you may not understand, again its comparing system with system, naming with naming:
GIA gives you table size, total depth, while HRD gives you table size, crown height and pavillion depth, while you can calculate total depth yourself from the measurements. When giving girdle size, HRD uses another notation than GIA, and because of that the girdle will appear about 1.7% thicker on a HRD-report than on a GIA-report'
Some other reputable labs in my opinion:
HRD
IGI
EGI
AGS
To sum it up, HRD or any of the other labs are not a less reliable lab than GIA, as long as you are aware of some basic differences. In the end, it all comes down to where you are buying the stone. You need to buy it from a person, who can check a report, and who is professional enough to interpret that report, and if this does not suffice, you can still work with a professional appraiser.
