The Diamond Pro

IGI Certification: The Main Reasons We Don’t Recommend It

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Bottom Line Recommendation:

While IGI bills itself as a top-of-the-line laboratory, in our experience, this is sadly not the case. Their grading is laxer and less consistent than the standard bearers in the industry.

We recommend only buying a GIA or AGS certified diamond. We also recommend purchasing your diamond from a reputable vendor such as Blue Nile, Brian Gavin Diamonds and James Allen. James Allen does sell IGI certified diamonds, but we do not recommend those. The point of buying a diamond with an independent certificate is to get peace of mind that the diamond is the quality they claim. We feel that an IGI certificate does not deliver that.

History of IGI

Founded in 1975, the International Gemological Institute (IGI) began as the blue collar workhorse of the diamond business. As a large independent worldwide gemological laboratory, they’re headquartered in Antwerp, Belgium but have offices all over the world.

For major jewelry chains in the United States and Canada—like Kay, Zales and others—the IGI is the most popular gem lab. In a way, IGI is like a factory: they work fast, and their prices for grading are better than those of GIA—which appeals to diamonds sellers but not necessarily the end consumer.

Through our extensive experience in the diamond industry, we’ve continually noticed that their grading is lax and less consistent than the standard bearers in the industry, like the GIA.

IGI Diamond Grading Report

As an independent grading entity, the IGI evaluates each gemstone based on various qualities and components.

Grading Results and Scales

A diamond’s 4 C’s (Cut, Color, Clarity and Carat) represent the main characteristics of its structure and beauty. Each element is graded on a scale and the gradings help determine the value of a diamond and indicate its quality.


Cut represents the quality of a diamond’s angles, proportions, symmetrical facets, brilliance, fire, scintillation and finishing details.

The IGI uses Ideal, Excellent, Very Good, Good and Fair as its grade designations.


A Diamond’s Color grade determines how colorless it is.

The IGI grades color on a D-Z range with D being colorless and Z being mostly yellow/brown.


A diamond is graded for how free it is from inclusions and blemishes.

IGI evaluates diamonds from internally flawless to imperfect on the following scale.

  • IF (Internally Flawless)
  • VVS1 (Very, Very Slightly Included 1)
  • VVS2 (Very, Very Slightly Included 2)
  • VS1 (Very Slightly Included 1)
  • VS2 (Very Slightly Included 2)
  • SI1 (Slightly Included 1)
  • SI2 (Slightly Included 2)
  • P1 (Imperfect)
  • P2 – I2 (Imperfect)
  • P3 – I3 (Imperfect)


Carat refers to the weight of a diamond. As an example, 2 Carat Diamond equals 400 milligrams, or 0.4 grams—weighing about the same as a half of a raisin. The IGI report provides a precise diamond weight, down to the hundredth or thousandth of a carat.

Proportions and Symmetry

Also impacting the beauty of a diamond are its proportions, like the table, crown, pavilion, depth and culet.

An IGI report provides the details of these characteristics, helping to determine the quality of the diamond.

Proportions chart for IGI cetificate

Putting IGI Grading to the Test

We decided to put IGI to the test, given the conflicting reports about their reliability. We purchased five IGI certified diamonds and sent them to the gold standard of laboratories: GIA.

The results were predictable and unfortunate.

IGI inflated the qualities in eight of the ten possible grades (Color and Clarity on each diamond). Here are the results:

DiamondIGI GradeGIA Grade
1.04 ctK, SI2K, I1
1.02 ctI, SI2J, I1
1.15 ctK, SI2L, SI2
1.02 ctI, SI2J, I1
1.00 ctJ, SI2K, I1

*Click on the carat weight for a video of each diamond. Click on the color/clarity grades for respective certificates.

In our opinion, IGI simply does not function at the standards that reputable diamond laboratories hold themselves accountable to.
Below we will explain why this matters to you, the consumer.

Why Should You (the Consumer) Care About Consistency and Reliability of Grading?

The reason you must buy a diamond with legitimate certification is to give you peace of mind that the diamond you’re purchasing is the quality the seller is claiming it to be. A reliable certificate allows you to compare the diamond to similar diamonds and verify you’re receiving a fair deal.

The main problem with IGI is that we don’t believe they deliver reliable grading results. In fact, we feel that you’re likely getting a subpar deal if someone is selling you an IGI certified diamond. Take a look at these two searches of SI2 and I1 diamonds for comparison:

James Allen Search of SI2 one caraters.
James Allen Search of I1 one caraters.

A typical one carat SI2 diamond will end up costing you around $4,000. A typical one carat I1 (with all other specs being equal) will cost about $3,000.
Now, let’s say you come across a jeweler who sells IGI certified diamonds.

You see an I SI2 diamond for $3,500 and you think, “Wow, I’m saving about 20%!” In reality though, we feel the jeweler is deceiving you, and you are overpaying by about 20% with a certificate that inflates the quality claims (based on our and other expert’s observations).

This inflated grading approach is the oldest trick in the book, and it is used by companies to increase their margins while tricking uneducated consumers by using less strict grading certificates.

How Diamond Companies Play the Game

The diamond industry has seen the competition grow fiercer and the margins grow slimmer, but too many vendors and individuals choose the route of manipulation and trickery. They come up with alternative ways to increase their margins by providing unique experiences or special products. Diamond companies can, and do, cherry pick the results—using looser certificates with maximum grade inflation.

Here is another “trick” they use.

In our experience, some IGI laboratories are weaker graders than others. Many jewelers in America will say something like, “Oh, those IGI articles are talking about IGI in Botswana or Mumbai or Antwerp. The IGI lab in NY is much stricter.”

And in a way, that’s true. Unfortunately, those same jewelers play a simple trick. What they often do is take a diamond that has an IGI Mumbai (or Botswana, or wherever) certificate, and send it to IGI NY with the certificate from Mumbai.

Then, the seemingly stricter IGI lab in NY will give you a certificate and “honor” the grades from their sister laboratory.

We tested this rumor by sending the same five diamonds to IGI labs in New York, Mumbai and Antwerp. By comparing the grading results, we are certain these tricks are used. Three of the diamonds did not have a laser inscription from the IGI labs in Mumbai. Two of them did have laser inscriptions from IGI Antwerp.

We sent the three without inscriptions as “new diamonds” and sent the two that had inscriptions with the certificates from IGI Antwerp. Predictably, IGI New York downgraded the three “new diamonds” from their previous grades from IGI Mumbai, but matched the very generous grades from IGI Antwerp on the other two stones.

What does this tell you about their credibility? What does it say about a jeweler who uses IGI?

Unless it was a miraculous coincidence, IGI New York clearly honored the looser IGI Antwerp’s grades. In what way does doing this inconsistency help the consumer in their decision-making? And in what way does it provide credibility to IGI as an independent laboratory?

Legitimate laboratories do not let anything influence their grading (GIA ignores any markings you put on the packaging other than your own SKU number and weight). The GIA wouldn’t let someone tell them the grades of another GIA laboratory in hopes of influencing their decision.

Even though the industry knows about this trick, we were still surprised it worked so easily, so we decided to test IGI again—this time with a more precise methodology.

We took 4 diamonds already certified by IGI New York and we sent them to IGI Antwerp for certification as uncertified new diamonds. After getting the results, we sent these diamonds back to IGI New York with the Antwerp certificates attached (with the intention to influence the new grades). IGI New York was not made aware of the original IGI New York certificates that we had made.

Below are the results of our experiment:

DiamondIGI NY 1st TimeIGI AntwerpIGI NY 2nd Time
0.37ctI, SI2G, SI1H, SI2
0.37ctI, SI2F, SI1G, SI2
0.33ctG, SI2F, SI1F, SI2
0.30ctH, SI2G, SI1G, SI1

On one hand, it’s refreshing to see that IGI New York didn’t stoop so low as to match the ridiculously upgraded grades from Antwerp. On the other hand, they were clearly influenced by the accompanying Antwerp certs. Each stone received at least one upgrade.

Reviewer’s First-Hand Experience

Based on years of professional experience, we have personally selected thousands of diamonds to be sold as IGI SI2s at the major jewelry store chains in the US and UK.

In this selection program (usually the middle-ground price point offering great value as it’s the cheapest of the eye-clean grades), all diamonds have a minimum of SI2 clarity.

For these programs, we would strive to find diamonds that were in that “SI3” sweet spot—diamonds that would not receive an “SI2” from GIA, but were too nice to sell as an “I1.” This is our opinion based on years of experience.

If You’re Still Not Convinced on How IGI Certification Impacts Cost

On Nov 3rd, 2016, we performed a search on Rapnet (the world’s largest online market for wholesale diamonds—think: the NYSE for diamonds) using their TradeScreen™ tool. This tool allows you to capture a snapshot of average market asking prices for specific parameters.

We limited our search to 1 carat “triple excellent” round diamonds with no fluorescence. One search was limited to GIA certified diamonds only and the other search was limited to IGI certified diamonds.

See the results below:

Grid of GIA Certified Rap Discounts

Grid of GIA Certified Rap Discounts (Click to Enlarge)


Grid of IGI Certified Rap Discounts (Click to Enlarge)

Taking the average of the differences of all of these specific color/clarity combinations (weighing each coordinate on the matrix equally), leads to the conclusion that GIA certified diamonds are 18.77% more expensive than IGI certified diamonds on average (at least for 1.00-1.49ct diamonds).

In financial economics, the efficient-market hypothesis states that asset prices fully reflect all available information.

Based on all of our experience and tests, we feel there is only one logical explanation why the wholesale diamond market prices such an enormous discount for IGI certified diamonds compared to GIA certified diamonds: the “market” believes IGI’s grades are inflated when compared to GIA’s.

Advantages of IGI Certification

  • Informs you that you should look at a different diamond, and perhaps even a different vendor (one that sells GIA and AGS certified diamonds)
  • Certificate is given by the largest laboratory certification for diamonds and jewelry

Disadvantages of IGI Certification

  • Lacks grading consistency and reliability
  • Some IGI locations will grade a diamond loosely, while others more strictly (creating further inconsistency)
  • Does not provide peace of mind that you are getting the quality that’s claimed
  • May not be accurate
  • Not respected in the diamond industry

Unique Reports and Additional Services

In addition to diamond reports, the IGI offers jewelry and colored stone reports. The IGI also provides a global grading scale for Tanzanite, called the Tanzanite Quality Scale (TQS).

When it comes to purchasing a diamond, we do not recommend one that is IGI certified. Instead, we recommend buying a GIA or AGS certified diamond. We strongly suggest choosing a diamond from a reputable vendor like Blue Nile and James Allen.

Top Recommended Vendors
Blue Nile Blue Nile is the largest and most well known internet jewelry seller. They have the industry-leading largest available exclusive online inventory. Their high quality images are catching up to James Allens' and their prices are amazing.
What we love about them:
  • No questions asked returns within 30 days of shipment. Blue Nile will send you a paid shipping label to return the ring.
  • Lifetime Warranty
  • Free Shipping
  • Free prong tightening, repolishing, rhodium plating and cleaning every 6 months
  • Provide insurance appraisal
  • One free resizing within the first year of purchase
  • High quality images of about half of their diamonds
  • 24/7 Customer Service
  • 100% credit towards future upgrades (must be at least double in value)
  • Best in class fulfillment

James Allen James Allen is the leader in online diamond sales. Their imaging technology is at the point where it's almost the same as inspecting a diamond with a jeweler's loupe. Their customer experience is best in class, and they have recently upgraded their non-engagement jewelry inventory as well. They just unleashed their once-a-year 25% OFF Black Friday sale early!
What we love about them:
  • No questions asked returns within 30 days of shipment. James Allen will send you a paid shipping label to return the ring.
  • Lifetime Warranty
  • Free International Shipping
  • Free prong tightening, repolishing, rhodium plating and cleaning every 6 months
  • Provide insurance appraisals
  • One free resizing within 60 days of purchase
  • Free ring inscriptions
  • Best-in-class high quality imagery of all diamonds in stock
  • 24/7 Customer Service
  • Best-in-class packaging

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