Diamond Grading Labs and Pricing

40 years ago grading reports were only done for the finest quality diamonds. But today even very low quality larger diamonds sold in Wal-Mart come with a cert. Demand for skilled graders is intense. The most skilled grade higher quality stones, and since grading is a human skill, accuracy is an issue.

The GIA and HRD are not for profit organizations and are often perceived to be the most independent. The AGS lab is half investor owned, and half owned by an association of up market jewlers. AGS specializes in grading better cut round diamonds and this is why AGS stones are the most expensive. The other labs are privately owned.

Imagine a cutter or merchant might send a stone to GIA if it is a certain VS2. A soft VS2 may go to another lab hoping that they may pass the stone as a VS2 (a GIA SI1 would sell for less). Pricescope challenge all labs to fund an independent survey (we would supervise) to compare various lab grades.

See results of Pricescope' independent Diamond Grading Laboratory Survey conducted in April-June 2004.

Data for July, 2004
% Price difference
compared to GIA
better cut rounds
Ex/Ex Pol/Sym
59% - 63% Depth
53% - 58% Table
GIA 0% -5.7% -15.7%
AGS +6.5% +5.5% -
EGL-USA -9.1% -14.8% -18.5%
EGL (Overseas) -13.0% -17.3% -21.4%

Merchants send stones to AGS that they believe will get a cut grade AGS 0 or 1 (on a scale of 0 to 10). Stones with lower AGS grades are rare. But diamonds with other certs can also score very high on HCA and not all AGS 0’s score excellent or very good. Merchants may have volume deals with one or two labs; they may never send stones to AGS. It is common to have an AGS cut grade supplied by the dealer on better cut diamonds certified by other labs. This is commonly in the form of a 2 x 1 inch label stuck onto the ‘paper’ the diamond is stored in. The diamond has not been sighted by AGSLab, the stone has been Sarin or Ogi scanned by the vendor. The information is usually accurate.

EGL invented the SI3 grade which brings them extra grading business for better I1’s and stones the dealers think might be border line SI2 / I1’s. With a close look you can usually spot inclusions. EGL-USA has a legal trademark battle raging with EGL, who operate mainly in Israel and Belgium. EGL has a reputation for softer grading while the US / Canadian owners have tightened up (which is reflected in the pricing comparison). EGL-USA certs are clearly labeled as such, but on internet data bases it is difficult to tell which is which without viewing a copy of the actual scanned cert (not a dummy web form).

HRD is the Belgian equivalent of GIA. HRD certified diamonds are more common in Europe and the East.

Populations of HRD and IGI graded diamonds on the internet are too small to make a price comparison, but in the trade round diamonds they have graded may be similar to GIA and EGL-USA respectively.

The AGA lab is a small regional east coast respected firm. They specialize in fancy shape diamond cut grading.

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