Which Diamond Grading Certificate is Best? Don’t Buy the Certificate!

February 10th, 2010 by James L. Sweaney, CGA, FGA. GG

We posted this about a year ago–with the tough economy, this insider information is more pertinent than ever, so we've tweaked the original blog a bit–here it is again.

In their quest for the best value, consumers looking to buy a diamond often make the mistake of giving equal weight to diamond grading certificates. Diamond grading certificates/reports are issued by various laboratories for the purpose of identifying, measuring and weighing, and grading a particular diamond. These reports are not appraisals.

One problem is that even though the various labs all use the diamond grading system/language developed in the 1950's by the Gemological Institue of America (GIA), each lab has its own internal methods, standards, experience and skill levels.

Another issue is independence. The GIA decided early on that their lab should be a disinterested third party, independent of the buying and selling of the gems. To this day, GIA is very careful to maintain the “arms length' rule and does not participate in buying, selling, or appraising diamonds or colored gemstones in any way. However, all labs, including GIA, do charge for their expert grading services–the fees are usually paid by the diamond merchants who own the stones.

Many of the other labs are profit making and some are closely affiliated with the firms for whom they grade diamonds–and this relationship is not always apparent to the ultimate consumer. The important thing to remember is that even though diamond grading reports/certificates may look very similar, but the quality of the information can vary significantly. Our case history reported below shows just how much this disparity can mean in dollars.

GIAsamplecertEGL report

Consumers tend to shop by comparing prices using the grades stated on grading certificates as their basis of comparison–the internet makes it very easy to do this. The grading reports all look the same and have what appears to be the same information, so this seems like a fool proof way to shop prices.

A stone graded SI1 F by one grading laboratory sells for 30% less than a stone of similar weight graded SI1 F by another grading laboratory, so you buy the less expensive stone. You

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One Response to “Which Diamond Grading Certificate is Best? Don’t Buy the Certificate!”

  1. LH Says:

    OK, well said and very helpful. The more research I do, the more it seems like GIA is the best grading certificate. I know you mentioned another lab, but from everything I’ve been reading most people say GIA is the most trustworthy, has the best reputation and the strictest grading.

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