What rough % of polished diamond production is lab graded?


Jun 10, 2014
Hello there,

Do we know roughly what percentage of polished diamonds on the market annually are GIA/HRD/AGS graded (or just any one of those labs)?

I've done a search on here and even though I'm sure there is relevant information somewhere, I can't find it. Stats on the proportion of output that grades to certain certain levels on the 4Cs would also be really interesting. I'm trying to get an evidenced handle on what proportion of polished diamond production is accounted for by stones with an excellent cut and colour and clarity of J and SI1 and better (or a similar but differently drawn set of criteria). I've found data relating to carat size, but not the other characteristics.

This enquiry is prompted by one of the many discussions on "rarity" that arise whenever diamonds are mentioned.

Any links or input gratefully received!


Nov 6, 2008
Re: What rough % of polished diamond production is lab grade

I can't help you, but hopefully someone on here can, because I love this question! Very interesting, I'm curious now as well.


Jan 7, 2009
Re: What rough % of polished diamond production is lab grade

Interesting question for sure.

We need to qualify the phrase "polished diamond production" a bit.
If we include teeny diamonds it totally changes the numbers.
Are we speaking of number of stones ( more relevant IMO) or total carat weight.

Here's a sample I just complied, using these search parameters plugged into the wholesale database.
Search parameters:
Shape, Any
Size .25ct-100.00 ct
"Any" color, clarity, etc
Result, is 1.08million +- individual stones
Filter by checking the GIA/AGSL/HRD box we get to 875,000+- diamonds

That's a fairly high percentage....but of course many of the diamonds sold never get listed on the wholesale database at any time.
Many stones offered at mall and jewelry B&M stores never get listed on he database- as well as many stones on the higher end.

If I filter GIA only we get about 840k stones
AGS only= 6500+- stone- wow, rare. Less than 1% of GIA

For whatever it's worth.


Jul 21, 2004
Re: What rough % of polished diamond production is lab grade

I've actually tried to answer this question for years. It seems vaguely important but I”ve been stymied at several steps. Here's the problem:

Production: The majority of diamonds are industrial and the exact details of the demising line between gem grade and industrial is both unclear and proprietary. 'Chocolate' diamonds, for example, used to be sold to the industrial market. Now they're gems. The majority of gem diamonds are little, under 0.10cts. Lab grading, as you're thinking of it, obviously doesn't apply here. This means an arbitrary cutoff for size and grades need to apply. In general, the bigger and better the stone, the more likely it is that the labs will be involved.

History. Roughly speaking, every diamond ever mined is still out there. Labs have only been king of the roost for about 15 years. That makes for a lot of diamonds that were produced in a time when labs weren't even one of the options. They can and do get submitted but it makes for a difficult problem in reconciling mining statistics with lab statistics.

What's a lab? Every stone is graded by someone. Usually many times. Every time it's sold someone is making a grading claim from the minehead to the final customer's finger. Almost always it comes from an expert. Sometimes this is written down, sometimes it's not. Sometimes it's the seller making the claim, sometimes it's an independent grader. IGI, an undisputed independent lab company, has grading operations inside many of the cutting factories. Depending on their results, a stone might get reworked to 'fix' something and then be reexamined. Depending on their results, it might get sent on to a different lab, it might get sold with a variety of different IGI documents, or it might get sold with no documents at all. Does this count? If an independent expert sorts 0.01's based on grade so that they can be priced accordingly, does that count?

Some stones get graded repeatedly. As with the above, this screws up the statistics when reconciling the mine data with the lab data. If the client doesn't like the results they can and do send things to a different lab. They can and do send them back to the wheel to tweak something and then try again. The lab would call each iteration of this a different stone when, in practice, it's the same stone over and over again. Just because somebody somewhere submitted a stone to a lab, or many labs, doesn't mean you will ever see any of those documents.

At the end of all of this, and in making some assumptions, lets say only stones over a carat, expected over I1, expected over L, and sold within the last 15 years, I think the answer is that most have seen at least one lab that produced an individual document about it. For stones over 2 carats, over I-1, over J, and from a relatively recent mine production, I think it's close to 100%.

FWIW, whatever the answer, it's clearly increasing. The importance of lab papers at both the wholesale and retail level has been increasing continuously for decades. The lab companies, like GIA and IGI are among the most successful in the industry and, paired with Rapaport, Polygon, IDEX and other data handling companies, have completely rewritten the way diamonds change hands.


Apr 24, 2015
Re: What rough % of polished diamond production is lab grade

Really depends on the size, color and clarity. Half carat and above I would expect more than 75% of diamonds to be lab graded by ANY lab. That percentage increases with the size. But stones in I1-I3 clarity grade don't happen to be graded too often.
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