SI stands for Slightly Included: the two clarity grades (SI1 and SI2) where a grader sees inclusions easily under 10x magnification, and where some of them start to show to the naked eye. An SI1 diamond is often eye-clean; an SI2 often is not. SI is the value grade in mined diamonds, where it can cost far less than VS. In lab-grown diamonds the saving is small, which is why Clairamor does not stock SI: every stone in our picker is VS2 or better for a few percent more.
SI diamonds at a glance
| Attribute | Detail |
|---|---|
| Full name | Slightly Included, grades SI1 and SI2 |
| Position on the scale | 7th and 8th of 11 grades, below VS2 and above I1 |
| Under a 10x loupe | Inclusions are noticeable (SI1) or easily noticeable (SI2) |
| To the naked eye | SI1 is often clean in brilliant cuts under 1.5 ct; SI2 often shows something, especially in step cuts |
| Typical inclusions | Crystals, feathers, clouds, twinning wisps, needles; the type and position decide visibility |
| Price | Mined: a large discount to VS. Lab-grown: a small one |
| At Clairamor | Not stocked; the picker starts at VS2 |
What does slightly included mean?
Every diamond is graded for clarity under 10x magnification against the Gemological Institute of America's eleven-grade scale. The grader records each inclusion (a feature inside the stone) and blemish (a mark on the surface), then weighs five things: how many there are, how large, where they sit, what kind they are, and how much they stand out against the diamond around them. GIA defines the SI grades as inclusions that are noticeable to a skilled grader under 10x.
That definition is about the loupe, not the eye. Nothing in the SI grade says an inclusion is visible without magnification. What separates an SI stone you would happily wear from one you would not is the specific inclusion: a white feather tucked under a prong is invisible; a dark crystal in the middle of the table is not, even in an SI1.
The rest of the clarity scale, for reference. VVS1 and VVS2 (Very, Very Slightly Included) are grades a grader struggles to find anything in. VS1 and VS2 (Very Slightly Included) have minor inclusions found with effort. I1, I2 and I3 (Included) have inclusions obvious at 10x that can affect transparency and sparkle. Our guide to VVS1 clarity walks the top of the scale; this one covers the bottom of the eye-clean range.
The diamond clarity scale, cleanest on the left
Visible to the naked eye?
Clairamor stocks IF through VS2. SI sits just past the line where inclusions can start to show.
SI1 vs SI2: how different are they?
More different than the one-step gap suggests. SI1 is the last grade where most stones are still eye-clean; SI2 is the first grade where most are not. The grader's language is the tell: SI1 inclusions are "noticeable" at 10x, SI2 inclusions are "easily noticeable", and easily noticeable at 10x often means visible at 1x if the inclusion is dark or sits under the table.
| SI1 | SI2 | |
|---|---|---|
| Under 10x | Inclusions noticeable | Inclusions easily noticeable |
| Naked eye, round or oval under 1.5 ct | Usually clean | Often a visible mark |
| Naked eye, emerald or Asscher cut | Frequently visible | Almost always visible |
| Naked eye, 2 ct and up | Check the stone | Expect to see it |
| Effect on sparkle | None, unless graded on clouds | Dense clouds can dull it |
| Buying rule | Fine if you have seen the stone or its video | Only with an eye-clean guarantee |
SI vs VS vs VVS: the three "included" tiers
The names confuse everyone, so here is the whole middle of the scale in one place. Very, Very Slightly Included (VVS1, VVS2) means a grader can barely find the inclusions. Very Slightly Included (VS1, VS2) means minor inclusions found with some effort. Slightly Included (SI1, SI2) means the grader sees them without effort. The eye cannot tell VVS from VS. It can sometimes tell VS from SI, and usually tell SI1 from SI2.
| Tier | Grades | Under 10x | Naked eye | Lab-grown price vs VS2 |
|---|---|---|---|---|
| Very, very slightly included | VVS1, VVS2 | Extremely to very difficult to find | Clean | A few percent more |
| Very slightly included | VS1, VS2 | Minor, found with effort | Clean in almost every stone | Baseline (Clairamor's entry grade) |
| Slightly included | SI1, SI2 | Noticeable to easily noticeable | SI1 often clean; SI2 often not | A little less; not stocked |
In Clairamor's own inventory on September 23, 2026, same-color VS1 and VVS2 rounds at 1 and 2 carats were $3 to $20 apart. Clarity moves lab-grown prices very little above VS2, and only a little below it, which is the whole argument of the next two sections.
Are SI diamonds eye-clean?
Some are. "Eye-clean" means no inclusion is visible to the naked eye from about six to twelve inches in normal light, which is how everyone but a grader will ever look at the ring. Whether an SI stone passes depends on four things the grade alone does not tell you.
- Type. A white feather or a small cloud disappears into the sparkle. A dark crystal, a black pinpoint cluster or a knot that breaks the surface does not. Twinning wisps are usually harmless; a dense cloud that earned the grade can make the whole stone look slightly milky.
- Position. Anything under the table (the big flat facet on top) is in the spotlight. Anything near the girdle can be hidden by a prong or a bezel. Graders plot every inclusion on the report, so you can see where they sit before you see the stone.
- Size and shape of the stone. Bigger facets are bigger windows. A 1 ct round SI1 hides what a 2.5 ct round SI1 shows, and an emerald cut shows what a cushion hides at the same weight.
- Color of the inclusion against the stone. A colorless inclusion in a D-color diamond is close to invisible; a dark one in the same stone is a spot.
The practical rule: never buy an SI stone from a grade and a price alone. Look at the plot, then at a video or the stone itself, and treat SI2 as visible until proven otherwise.
Which shapes hide inclusions best
| Shape | Faceting | How forgiving of an SI grade |
|---|---|---|
| Radiant | Brilliant, crushed-ice | Most forgiving; small inclusions vanish in the pattern |
| Cushion | Brilliant | Very forgiving, especially crushed-ice cushions |
| Round | Brilliant, 57 or 58 facets | Forgiving; SI1 rounds under 1.5 ct are usually eye-clean |
| Oval, pear, marquise, moval | Brilliant | Forgiving in the body; check the points and the center, where the bow-tie can frame an inclusion |
| Emerald | Step cut, large open facets | Least forgiving; treat SI as visible and stay at VS1 or better |
Not sure which shape you want yet? Our guide to which diamond shape looks biggest covers face-up size, and the size simulator shows each shape on a hand.
How much do SI diamonds cost?
In mined diamonds, SI is where the value is. Natural stones with few inclusions are rare, so each clarity step carries a real premium and an eye-clean SI1 can cost a great deal less than a VS1 of the same color and weight. That is why "buy SI1, save the difference for carat" is standard advice for natural diamonds, and it is good advice, provided you check the stone.
Lab-grown diamonds change the math. Growing conditions are controlled, a large share of production comes out at VS or better, and clarity is the smallest of the three price levers behind carat and color. Once the step from SI1 to VS2 costs only a few percent, the discount no longer buys enough carat to be worth the risk of a visible inclusion. Our lab-grown diamond pricing guide and price calculator show how the levers stack; the 4Cs guide covers how clarity fits with cut, color and carat.
Are SI diamonds worth buying?
For a mined diamond: yes, if it is an SI1 in a brilliant cut, you have seen the stone or a clear video, and the plot shows nothing dark under the table. Skip SI2 unless the seller guarantees it eye-clean and lets you return it if it is not. Skip SI altogether in emerald and Asscher cuts.
For a lab-grown diamond: no. The discount is small and the downside is a spot you will see every day. Our answer for every lab-grown engagement ring is the same one we give for VVS1: clarity should be the last lever you pull. Start with the shape, then the carat weight, then color, and let clarity sit at VS2 or VS1, where every stone is eye-clean and the price barely moves.
How to check an SI diamond before you buy
- Read the plot. On a GIA or IGI report, larger stones carry a diagram with a symbol for each inclusion. Red marks are internal, green are surface. Anything drawn inside the table outline deserves a close look.
- Read the comments. "Clarity grade is based on clouds that are not shown" is a warning that haze, not a single spot, earned the grade. Haze dulls sparkle and does not hide under a prong.
- Look at a 360 video in daylight-style lighting, not a single glamour shot, and pause it face-up. If you can find the inclusion on the video without the plot, you will find it on the finger.
- Match the inclusion to the setting. A feather near the girdle vanishes under a prong; a crystal near the edge can be hidden by a bezel or a hidden halo.
- Ask for an eye-clean guarantee in writing and confirm the return window. Our guide to diamond certification companies explains how to verify a report number online before you pay.
Where Clairamor fits
Clairamor sells lab-grown diamond engagement rings as a setting plus a stone you choose, and our diamond picker only lists stones graded IF through VS2 in D through G color, with GIA, IGI or HRD reports. That means you never have to run the checks above: every stone is eye-clean, and the few percent it costs to be above SI is the cheapest insurance in the ring.
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Frequently asked questions
What does SI mean in diamonds?
SI stands for Slightly Included. It covers two clarity grades, SI1 and SI2, where a trained grader can see inclusions without much effort under 10x magnification. They sit below VS2 and above I1 on the eleven-grade GIA scale.
Is SI1 a good diamond clarity?
SI1 is a respectable grade and often eye-clean, especially in round, oval, cushion and radiant cuts under about 1.5 carats. It is the value grade for mined diamonds. For lab-grown diamonds the saving over VS2 is small, so VS2 or better is the more sensible choice.
Is SI2 too low for an engagement ring?
Not automatically, but SI2 stones usually have an inclusion you can find with the naked eye, and in emerald cuts or larger stones you almost always can. Buy SI2 only with an eye-clean guarantee and a return window.
Are SI diamonds eye-clean?
Some SI1 diamonds are eye-clean and most SI2 diamonds are not. It depends on the inclusion's type, position and color, and on the stone's size and shape. The grade alone cannot tell you; the plot and a video can.
What is the difference between SI1 and VS2?
One grade, but an important one. VS2 inclusions are minor and found with effort under 10x, and VS2 stones are eye-clean in almost every case. SI1 inclusions are noticeable under 10x, and eye-cleanliness depends on the stone. VS2 is where Clairamor's picker starts.
Is there an SI3 clarity grade?
Not at GIA, IGI or HRD. SI3 was used by some other labs for stones between SI2 and I1. If a report says SI3, read it as a top I1 and grade the seller accordingly.
Do lab-grown diamonds come in SI clarity?
Yes, though a smaller share of lab-grown production grades SI than mined. Because the price gap between SI and VS is small in lab-grown, many retailers, Clairamor included, simply do not stock SI.
How much cheaper is an SI diamond than a VS diamond?
For mined diamonds the discount can be large, because natural stones with few inclusions are rare. For lab-grown diamonds it is small: clarity is the least expensive of the three main price levers, behind carat and color.
Can you see inclusions in an SI1 diamond?
Under a 10x loupe, yes, that is the definition. With the naked eye, often not in a brilliant cut under 1.5 carats. In a step cut, or when the inclusion is dark and sits under the table, you often can.
Which is better, SI1 or VS2?
VS2 is the higher grade and the safer buy. SI1 is the better value in mined diamonds if the specific stone is eye-clean. In lab-grown diamonds the price difference is small enough that VS2 wins.
Related reading
- VVS1 Diamond Clarity: Meaning, VVS1 vs VS1, and Is It Worth It?
- VS1 vs VS2 diamond clarity: what VS means, what you can see and what it costs
- Diamond color scale: D to Z chart, what you can see and what each grade costs
- How to buy a lab-grown diamond
- What is a tulip setting? Prongs, basket and cathedral explained
