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How to Buy an Eye Clean SI1 Diamond

Go beyond the certificate with our five rules for buying an eye clean SI1 diamond.

Conventional online diamond salespeople will tell you that if you’re looking to get a bigger diamond for your money, go low in clarity, medium in color and high in carat. You may hear that an SI1 diamond is the best value for your money — unless you’re buying a step-cut stone like an emerald or Asscher, which in that case, none of these rules apply.

Generally, SI1 is the lowest clarity grade recommended if you’re purchasing without you or a gemologist viewing the diamond in person to confirm that it is indeed eye-clean. If your shopping offline, and you see a shockingly low price, check the clarity. Mall chain jewelers will often fill their pre-set settings with lower clarity grade stones such as SI2 and I1. I1 is often marketed as SI3, but, the GIA doesn’t recognize that grade, and it’s misleading. At the mall chain jeweler, you’ll also find unnaturally bright LED lights to amp up the sparkle and mask inclusions. 

While you might think an SI diamond is the best value for money, the answer is often yes, but, not always. The reality is that while SI1 and SI2 diamonds can be a great value, and are often eye clean, they’re not always. Without reviewing the certification in detail, including the comments, it’s hard to know if you’ve scored a stunner or a bummer. If you’re thinking about purchasing an SI1 diamond online without backup from an expert, here’s what you’ll want to watch out for.

How to Read a Diamond Certificate

To understand inclusions, you need a quick tutorial on how to read a grading certificate. Gemologists list inclusions in order of severity. The top inclusion is generally the main reason for the clarity grade it receives. GIA certificates also include a diagram that showcases the location and type of inclusions. Here’s a guide you can use to as a legend. IGI and GCAL certs don’t include a diagram depicting inclusion locations, so you’ll have to rely on your eyes, the video, or the help of an expert.

When purchasing a lower clarity diamond, you’ll first want to look at the certificate and understand where the inclusions are located. Are they in the middle of the table or near the edge? Sometimes you’ll find an SI1 diamond that could be a VS2 or VS1 if it weren’t for a large inclusion on the girdle. If you’re shopping for a bezel setting, it could be your lucky day, because that inclusion might be hidden under the slim metal band surrounding the diamond. This is one way to get a much larger diamond than you’d initially anticipated. 

A GIA grading certificate showing an SI clarity diamond

The Dreaded Black Inclusion in an SI1 Diamond

As we mentioned earlier, not all SI1 diamonds are eye-clean. According to the GIA “(SI) diamonds have noticeable inclusions that are easy to very easy for a trained grader to see when viewed under 10x magnification. The SI category is divided into two grades; SI1 denotes a higher clarity grade than SI2. These may or may not be noticeable to the naked eye.

Sometimes inclusions are white. White inclusions are usually very hard to see without magnification. Sometimes inclusions are black. If you’ve seen a trendy salt and pepper diamond – that’s what you’re looking at. There are even certain types of inclusions that come in black and many other colors of the rainbow.

If you’ve ever heard of salt and pepper diamonds, the pepper — black inclusions. The salt — white inclusions. These diamonds are so included that they aren’t graded by traditional diamond grading labs. They are also extremely vulnerable to cracking and chipping.

A salt and pepper trillion cut diamond
A salt and pepper trillion rose cut
A slat and pepper tapered baguette diamond
A salt and pepper tapered
baguette diamond

These are a few of the more common types of black inclusions you may encounter on a diamond cert —


Let’s talk about the dark crystal. No, we don’t mean the movie. While crystals don’t sound bad, crystals are minerals embedded in the diamond. White crystals can be nearly impossible to see. Black, red or green crystals — much more conspicuous. 


Pinpoints are tiny white or black crystals embedded in a diamond. On their own, they’re very hard to see, even under magnification. In a group? That’s where the problems begin. Learn how to decode other types of inclusions commonly found in SI clarity diamonds in our guide.

Location, Location, Location

An inclusion’s location can be equally as problematic as it’s appearance. With step cut diamonds like Asscher’s and emeralds, it is much easier to see inclusions. If you’re in the market for a step-cut diamond, focus your attention on the table of the diamond. You’ll want to be sure to purchase one with a clear table. Brilliant cuts like the round, oval, pear, and marquise are much more forgiving, but, a black inclusion in the center of the table is still going to show up to the naked eye.

An SI1 diamond with a black inclusion in the middle of the table
An SI1 diamond with no black inclusions on the table

“Clouds Not Shown”

Clouds can dull a sunny day, and they can also dull a diamond. If you look at a GIA or IGI diamond certification, you’ll see a spot reserved for comments. One comment frequently seen on SI1 diamond certificates is “diamond clarity grade based on clouds not shown.” Do not buy an SI clarity diamond that has this on the certification. These diamonds will likely appear milky or cloudy to the naked eye due to the presence of clusters of pinpoint inclusions, called clouds, throughout the diamond. They block light and cause it to look dull.

Internal Graining

Think stretch marks. Internal graining is a result of distortion within the carbon lattice which causes faint lines. This can occur in natural and lab grown diamonds. Similar to clouds, in higher clarity diamonds internal graining is a non issue, but in SI diamonds it can cause a diamond to look hazy.

An SI2 lab grown diamond with internal graining

A Suspiciously Clean Plot Map

If you’re looking at a GIA cert for an SI1 or SI2 diamond and it has a suspiciously clean plot map, keep looking. This is a telltale sign that something is off. It could be milky, have a funky tint, or be based on clouds or twinning wisps not shown. 

Can you spot the issues with the plot map below? At first glance, this looks like a relatively OK SI1 for a yellow gold setting. While there is an inclusion in the middle of the table, this can be OK for brilliant cuts depending on the type of inclusion. However, digging deeper, we see that the main inclusion listed is a crystal. What color is the crystal? We don’t know. Furthermore, looking at the comments section we see a second problem. The grade is based on clouds not shown. It’s likely that this diamond is cloudy with a colored crystal in the center of the diamond. Is that an SI diamond that you’d want to purchase blind? No.

So to recap. If you’re thinking about buying an SI1 diamond or SI2 diamond online, and you want to DIY it here are some guidelines to follow.

Five Rules of Thumb for Buying an SI1 Diamond

If the plot map looks suspiciously clean – keep looking.

If the clarity grade is based on clouds not shown — keep looking.

If the first inclusion listed is a crystal — make sure to see a video of the diamond to find out what kind.

If the diamond has black or colored inclusions — keep looking.

If the diamond has inclusions under the main table and is step-cut — keep looking.

Not sure if an SI clarity diamond is right for you? Check out our guide to clarity in which we do a head to head match up of the most frequently requested clarity grades. When in doubt, ask for a video or get our help. Diamonds may be the hardest thing on earth, but we can help make buying them easier.

Ready to Find Your SI1 Diamond?

Check out our diamond search where you can view 360-degree images of more than 10,000 diamonds and don’t forget to zoom out (because size can be deceiving), or book a virtual or offline appointment at our New York salon to view certified lab-grown and natural diamonds in person. 

Not finding what you’re looking for? Email us with what you’re looking for at We’ll curate a list of 5-7 exclusive stones that are just right for you.

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