You can save real money by choosing an SI1 diamond but only if you know what to look for. SI1 sits right on the edge of what’s usually considered eye-clean. Around 45 to 55 percent of SI1 diamonds pass that test, depending on the shape and size. So this is all about playing the odds.
VS2 is safer but if you’re aiming for value without losing beauty, SI1 can absolutely work. You just need to filter more carefully. In this guide you’ll learn exactly how to find an SI1 diamond that looks flawless to the eye and gives you more diamond for your money.
What is an SI1 Diamond?
SI1 stands for “Slightly Included 1”, a clarity grade that means the diamond contains minor inclusions that are easy to spot under 10. magnification but often invisible to the naked eye. These inclusions can be feathers, crystals, clouds, or other natural imperfections formed during the diamond’s creation. You can read more about specific inclusions in my diamond inclusions guide.
In the clarity scale, SI1 sits just below VS2 and above SI2. VS2 diamonds are almost always eye-clean, while only about 10 to 15 percent of SI2 diamonds meet that standard. With SI1 diamonds roughly half are eye-clean, depending on the shape and inclusion placement.
In the table below you’ll see how eye-clean rates vary by clarity grade, along with the most affordable eye-clean GIA-graded 1.00 carat Excellent Cut G-color diamond we found on James Allen in May 2025:
| Clarity Grade | Estimated % Eye-Clean | Cheapest Eye-Clean Diamond | Notes |
|---|---|---|---|
| VS1 | 97-98% | $3,680 | VS1 diamonds are nearly always eye-clean. Inclusions, if present, are very minor and difficult to spot even under magnification. |
| VS2 | 85-90% | $3,320 | Most VS2 diamonds appear flawless without magnification. This is a safe zone for most shapes and sizes. |
| SI1 | 45-55% | $2,730 | Around half of SI1 diamonds are eye-clean. Look for small, well-placed inclusions outside the table area. |
| SI2 | 10-15% | $2,310 | Most SI2 diamonds are visibly included. Eye-clean examples do exist, especially in well-cut rounds but they’re harder to find as carat weight increases. |
That’s nearly a $600 difference between the virtually safe VS2 option and the 50/50 safe SI1 option. For larger diamonds or when compared to higher clarity grades like VS1, you could easily be saving over a thousand dollars. For buyers who are willing to do the work and inspect each diamond closely, even SI2 diamonds can be a viable option. I cover that in more detail in my SI1 vs SI2 diamonds article.
Eye Clean and Not Eye Clean SI1 Diamonds
Not all SI1 diamonds are created equal. Some will look completely clean to the naked eye, while others will have visible flaws right under the table. That’s why it’s important to understand what you’re really dealing with when shopping in the SI1 range.
SI1 diamonds can contain feathers, clouds, pinpoints, black crystals, or a mix of these. The type, size, and location of the inclusion all determine whether the diamond appears eye-clean. Two diamonds with identical specs on paper can look completely different in person or under magnified video.
In the example below, both diamonds are 1.00 carat, G color, SI1 clarity and Excellent cut. On the left you see a textbook example of an eye-clean SI1 diamond. There is a tiny white feather inclusion just under the table near the 3 o’clock position, but it’s faint and well-positioned. It blends in naturally with the facet structure and is practically impossible to detect in real life. This is the kind of SI1 that delivers excellent value without compromising on appearance.
On the right, however, is an SI1 diamond that is clearly not eye-clean. There is a dark crystal inclusion located right under the table at the 10 o’clock position, which draws attention immediately. Dark crystal inclusions are the most noticeable in everyday viewing, especially when they sit near the center of the diamond where light enters and exits the most. This is exactly the kind of inclusion you want to avoid when buying an SI1 diamond.
How to Score an Eye Clean SI1 Diamond
Not all SI1 diamonds are created equal and that’s what makes this grade both risky and rewarding. The key is to filter carefully and know what makes a diamond look eye-clean. Below are the most important concepts to help you find an eye-clean SI1 diamond without overpaying.
Consider the Diamond’s Size and Shape
The bigger the diamond, the easier it is to spot inclusions. That’s because larger stones have bigger tables and more visible surfaces. A 2-carat or 3-carat diamond is far more likely to show flaws than a 1-carat diamond, even if the inclusion type is the same.
When you’re viewing diamonds on James Allen or Blue Nile for instance, they’re all shown at the same magnified scale, so it’s easy to lose track of how big the diamond actually is. An inclusion that looks small and harmless in a 1-carat diamond may look much more noticeable in a 2-carat stone because everything is scaled up in real life.
Here’s a perfect example of a borderline eye-clean diamond. This 1.00 carat G-SI1 round has a white crystal inclusion just under the table, slightly off-center. Most viewers would never notice it without magnification, but it’s technically visible up close. This is the kind of diamond where you’re getting top value without obvious flaws.
Now compare that 1.00 carat borderline eye-clean SI1 to this 2.00 carat G-SI1 diamond with a nearly identical inclusion. In a smaller diamond, the white crystal barely registers. But here, the larger table makes it easier to spot. This is where eye-clean status becomes much less likely, even if the clarity grade is the same.
One small drawback of online shopping is that you don’t truly get a sense of the diamond’s physical size. That’s why it’s important to always remember that the same flaw can be eye-clean in a smaller diamond but visible in a larger one. Which is especially relevant for buyers of lab-grown diamonds who can often afford much larger sizes.
The shape also matters a lot. Round, princess, and radiant cuts tend to hide inclusions well due to their brilliant faceting. Step cuts like emerald or asscher, are more risky at the SI1 level because they have large, open tables and less sparkle to hide inclusions. There’s no bling to distract the eye. If you’re buying a step cut, consider a higher clarity grade like VS2. For the five most popular diamond shapes here’s how risky it is to buy an SI1 clarity grade:
| Shape | Risk Level for SI1 | Why | Safe or Not? |
|---|---|---|---|
| Round | Low | The excellent brilliance and intricate faceting hides most inclusions. Even a medium-sized white crystal inclusion like this (Real Image) directly under the table will not be visible. | Usually safe |
| Princess | Low | The sharp facets scatter lights across the surface, making inclusions harder to notice. | Often safe |
| Cushion | Medium | The mixed brilliance may or may not reveal inclusions. | Case by case |
| Emerald | High | Has a large open table and a longer rectangular shape that shows flaws clearly. Even with inclusions like this non-black example, the large open table of an emerald cut makes it easy to spot. | Risky for SI1 |
| Asscher | High | Same open table issue but also has greater symmetry and a deeper pavilion, so that flaws reflect multiple times in a mirror-box effect. Even a small inclusion like this can dominate the face-up view of an Asscher cut. | Avoid SI1 |
Round diamonds can sometimes even tolerate slightly darker or cloudier inclusions because their sparkle helps mask them, but in step cuts even light inclusions become easier to spot due to the clear and mirror-like surface.
Watch Out for the Inclusions’ Size, Color, and Location!
The clarity grade itself doesn’t tell the whole story. What really matters is how visible the inclusion is from above, especially when the diamond is viewed face-up in normal lighting.
Dark inclusions like black crystals or dense clouds are harder to hide than small white feathers or translucent pinpoints. Inclusions near the center of the table are much more visible because they sit in the most reflective part of the diamond. By contrast, flaws near the edge often get lost in the sparkle or can be covered by a prong.
One of the most egregious SI1 examples I’ve come across is this emerald cut diamond. It shows exactly how misleading the SI1 label can be if you don’t inspect the diamond closely. Not only is the inclusion dark and positioned dead center under the table, the most visible and reflective area, but the step-cut facet structure of the emerald shape does nothing to conceal it. There’s no brilliance to mask the flaw, no angle to redirect the viewer’s eye. Just a painfully exposed inclusion staring right back at you.
Grouped or clustered flaws can also be more distracting than a single inclusion, especially if they create a hazy area or interfere with light return. That’s why it’s important to consider not just what the inclusion is, but where it is and how it interacts with the diamond’s cut.
As a general rule, avoid diamonds with visible inclusions under the table, especially dark ones. These are the most distracting and the hardest to hide, even in a setting.
GIA vs IGI SI1 Diamonds
When it comes to SI1 diamonds, most shoppers immediately trust GIA (Gemological Institute of America) because of its long-standing reputation for strict and consistent grading. And for good reason, especially now that AGS, once seen as GIA’s main competitor, has officially merged with GIA and no longer operates independently. But in recent years, IGI (International Gemological Institute) has become a serious competitor.
IGI has exploded in popularity in recent years thanks to the rapid growth of the lab-grown diamond market, where it became the dominant grading lab due to faster turnaround times and lower certification costs. That trend gave IGI significant visibility among buyers, retailers and manufacturers.
But here’s what many shoppers overlook: IGI is also grading more and more natural diamonds, especially in online retail channels like James Allen and Blue Nile. While GIA still dominates for earth-mined diamonds, IGI is quietly gaining market share as more vendors list both options.
To see how this plays out in real listings, I filtered for GIA-graded 1.00 carat H-SI1 Excellent Cut diamonds and sorted by price from lowest to highest:
Then, I did the same for IGI-graded diamonds. The result is telling. Not only are the IGI diamonds clearly more affordable but surprisingly none of the GIA options in this batch were eye-clean, while two of the IGI stones were:
All three GIA diamonds have visible black inclusions. In the first GIA diamond, the flaw sits near the 7 o’clock position, while the other two have darker inclusions right in the center of the table. In contrast, the first two IGI diamonds show smaller, scattered inclusions that are not visible without magnification. Only the last IGI diamond has a visible inclusion between the 4 and 5 o’clock position.
So, am I saying that IGI’s grading is stricter than GIA’s? No. But it’s definitely worth filtering for IGI diamonds only and sometimes the results might surprise you. You may find a diamond that looks cleaner and costs less, even at the same clarity grade. The only downside is that IGI diamonds usually make up just 5 to 10 percent of the available inventory for any specific color and clarity combination, so your options will be more limited.
IGI isn’t dramatically looser across the board but it has historically been slightly more lenient than GIA in areas like color and cut (especially for fancy shapes). For clarity specifically, the gap is much narrower than most people think, which is why visual inspection always matters more than the label alone.
Our Key Takeaway
SI1 diamonds sit right at the edge where prices drop but risks rise. That’s why they offer some of the best value in the entire clarity scale, if you know how to pick the right one.
Not all SI1 diamonds are eye-clean. In fact, only about half of them are. But if you’re willing to inspect each stone carefully using magnified images and 360° video, you can find a diamond that looks just as clean as one graded VS2 or even VS1, at a much lower price.
For those who prefer to play it safe my VS2 diamonds article breaks down why that grade is often the sweet spot for peace of mind. If you’re open to taking a little more risk for a bigger reward, you might also find value in my guide to SI2 diamonds. And just as with clarity, you can save significantly on appearance by choosing the right diamond color. I cover exactly how to do that in my full-color guide.
As for where to shop, my most trusted and recommended vendors are Whiteflash for elite-cut precision and vetted craftsmanship, and James Allen and Blue Nile which offer the largest and most searchable diamond inventories online.
Pay close attention to the size, color, and location of the inclusions. Use trusted labs like GIA and always view the diamond yourself instead of relying on the report alone. And don’t overlook IGI. While they may have a more lenient reputation, many of their SI1 diamonds are clean to the eye and hundreds of dollars cheaper.
The bottom line: SI1 is a smart choice for buyers who want to maximize value without sacrificing beauty, but only if you’re willing to do the work. If you want a shortcut, VS2 is the safer bet. But if you’re reading this, chances are you’re the type who wants to shop smart. And for that, SI1 is where the real opportunities begin.