Is AGS Lax In Its Grading of Clarity as Compared to GIA?

Today’s Question: I’ve been reading up information on your website and I know that no two diamonds are the same. Based on your website’s recommendation, I’d been looking through James Allen and searching for a round diamond in the 1.50 carat range.

In their True Hearts selection, I came across this Si1 stone graded by AGS and was pretty surprised at how obvious the inclusions were showing up in the pictures. I had literally browsed through the entire collection of SI1 True Hearts stones and this seemed to be the only stone that stands out like a sore thumb. 

si1 round diamond graded by ags

Why does this SI1 diamond have obvious inclusions?

Unfortunately, the link to the stone diamond is already sold and delisted from JamesAllen’s inventory at the point of writing. That doesn’t stop us from asking the following question – Did AGS make a mistake with this diamond or are they relatively more lax in terms of their grading standard as compared to GIA?


Paul’s Reply: There’s a lot of misinformation on other “diamond advice websites” or forums where it is stated that diamonds in the SI clarity range will always be eye clean. I’m glad you wrote in with your question as this is a fine example which proves otherwise. When it comes to buying diamonds in the slightly included ranges, it is imperative for you to see the diamond with magnified pictures or with a 10X loupe if you are buying in person.

As you have said, every diamond is different. When it comes to buying SI diamonds, it is sometimes better to have an inclusion plot that looks messy rather than one with a single inclusion. This is because the probability of a single SI inclusion being noticeable is much higher compared to diamonds with inclusions that are well spread out.

To answer your question, I don’t think that AGS has made a “mistake” on calling this a SI1 stone. Based on the photograph alone, it seems to border closely to an SI2 grade. The major inclusion is found near the girdle edge at a slightly more inconspicuous location and I think AGS made the right call on this.

Here’s a Major Tip for Smart Shoppers

Every single SI diamond with clouds needs to be inspected with more scrutiny. This is because the plot in a lab report only indicates the position and “size” of the cloud but fails to tell you the density or color (white/black) of the cloud. Likewise, the same precaution should be undertaken for other types of inclusions like feathers or crystals.

cloud inclusion with high density

Dark black cloud that is visible to naked eye

In this example you had listed, the clouds are so dense it creates a dark patch that is visible without any tools. Did you know that clarity grades are also assigned based on the relative size of inclusion to the stone?

This means larger stones with a VS clarity might not necessarily be eye clean. For example, a 5 carat stone with VS2 clarity might have an inclusion that can be visible to the naked eye. The same exact inclusion in a 0.5 carat stone might cause it to be graded as an SI2.

Nonetheless, I think this is still a very well cut stone based on its Idealscope image and computer generated ASET in the grading report. While the cloud inclusion is prong-able, my advice for you is to skip this stone. There is no lack of better looking stones with a similar price point. If you need further help on choosing a diamond, please drop me another email in private.

Are you ready to shop for a proposal ring? Visit JamesAllen.com to browse through a collection of more than 30,000 GIA graded loose diamonds with high definition videos.

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One Comment

  1. Jospeh-
    December 15, 2012 at 5:40 pm

    Your website is a truly a refreshing read from many others that I had came across on the Internet. Thanks for contributing your knowledge and helping people like me who get really stressed up in buying diamond rings.

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