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Coping with diamond-grading discrepancies: What the H?!

By Mark T. Cartwright

Does any of this sound familiar?

  • “What do you mean J-colour, I-1 clarity?! The lab report says H-colour, SI-1!!”
  • “But when I bought it, the jeweller said it was two grades higher and worth way more than your appraisal!”
  • ”$10,000? You’re crazy. The guy across town has a diamond with a cert for $6500.”

As an independent appraiser who neither buys nor sells diamonds, I often have to explain why my grades are substantially different from those provided by a client’s grading report from one of the many laboratories. Inevitably, the client wants to know how something like this can happen. Come to think of it, aren’t we all a bit curious?

Recent and not-so-recent grading scandals at well-respected laboratories might cause the more cynical among us to assume the worst. I think it’s important to recognize that for the vast majority of the hundreds of thousands of diamonds passing through labs each year, a variance of a single grade rarely results in a significant difference in value. However, the same cynics may also believe deceitful practices are in play when some grading services reports are perceived to be consistently ‘optimistic’ in their grades.

I’ve always believed it’s really fairly easy to explain the root causes for most of the confusion, anger, and frustration felt by many trade members and a growing population of consumers over apparent discrepancies in diamond grades. Solutions are a bit more perplexing. In my opinion, the primary issue is a basic misunderstanding of what a ‘grade’ actually is. This misapprehension is exacerbated by the second problem of a shared terminology without a shared set of standards, grade boundaries, and methodology.

For the current discussion, we’ll limit ourselves to diamond colour grading, but it applies equally to clarity grading.

To gain a bit of perspective, maybe a little history is in order. The colour grading system, and its D ““ Z terminology as we know it today, was introduced to the jewellery trade by the Gemological Institute of America (GIA) in 1953 and integrated into its gemmological curriculum in 1954. It has undergone a few ‘tweaks’ over the intervening years, but is essentially unchanged. GIA initiated the clarity grading system at the same time, although it was referred to as ‘imperfection grading’ when introduced; the lab added the grades of ‘internally flawless’ and ‘I-3’ in the 1970s. Perhaps hoping to create a ‘universal language’ for diamond grading, GIA made no attempt to protect its intellectual property through patents, copyrights, or trademarks. While it has succeeded in establishing the ‘language of diamond grading’ beyond Richard Liddicoat’s wildest dreams, each laboratory appears to use a different dictionary to define the words we share.

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