Eye-Clean Diamonds, How to Find SI1 Stones That Look Like VS1

The single most exploitable gap in diamond pricing is one most buyers never hear about. An eye-clean SI1 and a VS1 with identical cut, colour, and carat will often look identical in normal wearing conditions, yet the VS1 can cost 25 to 40 percent more. On a 1.5ct G round brilliant, that's not a rounding error.

If you're still building your framework for evaluating diamonds, our diamond cut guide covers the full 4Cs picture. This post goes narrower: exactly how to find the SI1 stones that look like VS1, and which shapes make that hunt worth attempting.

Not all SI1 diamonds look the same

GIA grades diamonds at 10x magnification. SI1 means the grader can see inclusions at that magnification, but they shouldn't be visible to the naked eye under standard conditions. The trouble is, some SI1 diamonds are visible to the naked eye. The grade is a range, not a guarantee.

Eye-clean means arm's length, normal ambient lighting, naked eye, no inclusions visible. That's the standard. Not loupe-clean. Ordinary viewing, the way a diamond actually gets worn.

The grading system puts enormously varied stones in the same SI1 bucket. A needle inclusion near the girdle and a dark crystal dead centre under the table can both earn SI1. They do not behave the same way in real life. Knowing which SI1 to buy is what earns the savings.

The four factors that determine whether an SI1 is eye-clean

Inclusion type is the starting point. Needle inclusions, pinpoints, and tiny feathers near the edge sit at the benign end of the spectrum. Dark crystals and chips are the problem cases. Clouds occupy the most complex territory: a localised cloud is usually manageable, but when the GIA report comments "cloud, not shown," the cloud was too pervasive to plot individually. Pervasive clouds scatter light and can make the entire stone appear milky. Check the comments section of the report, not just the plot.

Inclusion size matters most in combination with location. A large feather near the girdle can still be invisible to the naked eye because the surrounding facets obscure the depth. A medium-sized dark crystal under the table has nowhere to hide.

Inclusion location is where the GIA plot becomes your most useful tool. The centre of the table, directly under the largest facet, is the worst position. The girdle, pavilion, and positions that fall under prongs in the finished setting are the best. The stone that looks identical to the VS1 next to it is often the SI1 with an inclusion tucked under where a prong will sit.

Diamond shape has the largest practical effect and gets the least attention. Round brilliants scatter and return light so aggressively that inclusions can disappear even when the plot shows them clearly. Step cut shapes, emerald cuts and asschers specifically, do the opposite. Their long parallel facets create large open windows that display what's inside the stone rather than masking it. The same inclusion that vanishes in a round becomes obvious in an emerald cut. Shape is not a minor variable. It's often the deciding one.

What the GIA plot tells you and where it hides things

The inclusion plot is a schematic overhead view of the diamond with standardised symbols marking each inclusion's type and position. Red symbols mark internal inclusions; green marks surface-reaching blemishes. The central oval represents the table facet.

Spend thirty seconds on the plot before you read the grade. A solid black dot means a dark crystal or mineral inclusion. In or near the centre of the table oval, that stone needs careful video review. Toward the edge, near the girdle line, the risk is much lower. A feather appears as a curved line; it's generally manageable if it's small and away from the table. A cloud that covers a meaningful portion of the plot is a concern regardless of position.

The specific GIA inclusion descriptors in the comments section matter too. "Feather" and "needle" in an SI1 are good signs. "Crystal" requires a location check. "Cloud, not shown" is the phrase to watch for, the one that doesn't appear on the plot but sits in the comment field. Our diamond clarity guide has the full reference on each inclusion type and what it means in practice.

Eye-clean rates by shape and clarity

The rates below reflect the proportion of stones in each category that pass the eye-clean standard, based on what we observe across the CaratHunter index.

Shape	SI1 eye-clean rate	SI2 eye-clean rate
Round brilliant (under 1.5ct)	60 to 70%	20 to 30%
Oval	50 to 60%	15 to 25%
Cushion	50 to 60%	15 to 20%
Pear	45 to 55%	15 to 20%
Princess	45 to 55%	15 to 25%
Radiant	45 to 55%	10 to 20%
Marquise	40 to 50%	10 to 15%
Emerald (step cut)	30 to 40%	Under 10%
Asscher (step cut)	30 to 40%	Under 10%

Round brilliants at SI1 pass more than half the time. Emerald and asscher cuts at SI1 fail more than half the time. Same grade, very different odds.

SI2 is a different conversation for almost every shape. The eye-clean rate drops sharply, and for step cuts it falls to under 10 percent. SI2 rounds can occasionally be excellent value because most buyers won't touch the grade. But they require proof. No video, no purchase.

How to inspect before you buy

Every serious retailer now offers HD video or full rotation footage. If one doesn't, move on.

The inspection workflow: watch the video at full screen at normal playback speed first. Don't scrutinise frame by frame. If something catches your eye in the first few seconds, note it. Most visible inclusions are obvious on first watch. Then pause at the overhead table view, where you see the full table facet straight on from above. That's the critical angle. Anything showing there will show in normal wear.

Cross-reference what you see against the GIA plot. A dark area at the centre of the stone in the video and a crystal marked near the table on the plot are almost certainly the same feature. If the video looks completely clean but the plot shows a significant inclusion under the table, ask the retailer for a second angle or a closer clip.

Loupe images, which many retailers include alongside video, show the stone at 10x magnification. They're useful for confirming inclusion type but not for assessing whether something will show to the naked eye. A stone that looks dramatic under a loupe can be perfectly eye-clean at arm's length. Don't let a loupe image rule out a good stone.

For SI1 rounds, expect to review 10 to 15 stones before finding one with a favourable plot, clean video, and the right price. For SI1 step cuts, the number is higher. The shortcut doesn't exist; the savings are the reward for doing the work.

Step cuts need VS1, not SI1

Emerald cuts and asscher cuts are extraordinary shapes. The hall-of-mirrors quality they produce is unlike any other cut. But those long step facets leave inclusions with nowhere to hide.

VS1 is the practical minimum for step cut diamonds. VS2 can work if you have video confirmation and the plot shows inclusions near the girdle only. SI1 in a step cut is a 30 to 40 percent chance of being eye-clean. You're more likely to see the inclusion than not.

The pricing gap between VS1 and SI1 in a step cut is real, and the savings are tempting. The problem is that you're selecting from a small subset of SI1 stones that happen to be eye-clean, and retailers don't price the favourable SI1 differently from the unfavourable one. The sorting is left entirely to the buyer.

A well-cut VS2 emerald with a favourable plot is almost always a better bet than an SI1 emerald that might pass. The eye-clean rate at VS2 is substantially higher, and the price difference between VS2 and VS1 is often modest enough to make VS2 the smarter compromise if the budget is tight.

A checklist worth running before any SI1 or SI2 purchase

Read the GIA comments section first. Flag any mention of "cloud, not shown" or "crystal, table area." Either phrase shifts the burden of proof onto the video.

Pull up the inclusion plot. Note where the inclusions sit. Anything plotted in the table centre region requires clean video confirmation before proceeding.

Watch the retailer video at full screen. Pause at the overhead table view. If you see nothing in that position, that's your primary confirmation.

Check inclusion type against the plot symbols. Needle, pinpoint, and girdle-positioned feather inclusions are good outcomes. Dark crystals and central clouds are where to stop.

For step cuts, apply the VS1 floor unless you have both clean video and a plot showing all inclusions near the girdle. The 30 to 40 percent eye-clean rate at SI1 means the odds are against you before you've even looked.

For SI2 in any shape, require video. The 20 to 30 percent eye-clean rate for rounds means most won't pass, but the ones that do can offer genuine value. Use the CaratHunter advanced search to filter SI2 rounds, sort by price, and run the inspection workflow on each candidate.

The 25 to 40 percent savings from a well-selected SI1 over a comparable VS1 are real. The work is real too, but it's learnable and finite. What we're watching going forward is whether automated clarity assessment tools start doing this workflow at scale. For now, the information advantage still belongs to buyers willing to read a plot and watch a video.