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On one end of the diamond clarity scale is flawless, where inclusions aren’t visible with 10x magnification. On the other end is I3, which indicates it has significant imperfections.
The main difference between SI1 and VS1 diamonds is SI1 diamonds have inclusions that are more impactful on its overall quality. The imperfections in VS1 diamonds often aren’t noticeable without magnification, so it appears flawless to the naked eye.
In fact, for my wife’s engagement ring, I bought her a round-cut VS1 diamond from James Allen.
But let’s compare SI1 versus VS1 diamonds, including an overview of each grade, their differences and similarities, and how to know which clarity grade is right for you.
What is an SI1 Diamond?
An SI1 (slightly included) diamond has inclusions visible with a standard jeweler’s loupe at 10x magnification. Sometimes they’re also apparent without magnification.
Here’s an image of an SI1 diamond.
On the GIA clarity scale, it’s one grade below VS2 and one above SI2.
The SI1 grade isn’t referring to any specific type of inclusion within the diamond, such as clouds, cavities, or indented naturals.
Instead, the gemologist combines a number of factors to determine the overall grade, such as:
- The size of the inclusions
- How they affect brilliance
The diamond is assigned a clarity grade based on these qualities.
In short, the inclusions in SI1 diamonds, compared to VS2, are more impactful. But they’re less so than ones that earn a lower grade.
For example, this 1.02 carat round diamond is from the vendor where I bought my wife’s engagement ring.
It earned an SI1 clarity grade, and you can view it in high resolution.
It has a few black spots scattered across its table, which are likely the result of crystalized carbon.
Other diamonds with SI1 clarity grades have several types of inclusions, such as crystals, needles, clouds, and naturals.
The GIA report includes a clarity plot that shows their size and position.
Obtaining a GIA report, or one from another reputable lab like the American Gem Society allows you to learn the details of its SI1 clarity grade before you buy.
What is a VS1 Diamond?
VS1 (very slightly included) diamonds have inclusions barely visible at 10x magnification.
Using a jeweler’s loupe, the gemologist may have to scan the diamond a few times before identifying any specific inclusions.
Similar to other clarity grades, a VS1 designation isn’t referring to any one type of flaw.
They may have etch channels, feathers, or a cavity.
It could be a combination of multiple inclusions, or several instances of one type.
As an example, this VS1 diamond has a crystal and a natural.
The clarity plot shows only one occurrence of each, and both are small.
These minor inclusions, combined with diamond weighing only 0.90 carats, means these inclusions aren’t visible to the naked eye.
The two inclusions kept it from earning a VVS (very very slightly included) clarity grade but aren’t enough to have a significant effect on the diamond’s appearance or brilliance.
In fact, if you placed a VS1 clarity diamond next to a VVS2 or VS2 diamond, you couldn’t tell the difference without magnification because the inclusions in all of them are minor.
What are the Differences Between SI1 and VS1 Diamonds?
1. VS1 Diamonds Have Fewer Inclusions
In most cases, VS1 diamonds have fewer inclusions than ones that earn an SI1 grade.
The number of blemishes is only one factor that determines clarity grade, but a high number will likely prevent the diamond from reaching the very slightly included status.
To illustrate, let’s compare two cushion cut diamonds. This one earned a VS1 clarity grade, and this diamond was graded SI1.
The GIA clarity plot shows the VS1 diamond has feather and pinpoint inclusions.
Both are so small they’re barely visible on the report.
There are two pinpoints toward the center of its table, and the feathers approach its edges.
If you view the diamond without magnification, you can’t see any of the inclusions.
The SI1 diamond, on the other hand, has five different inclusions:
- Indented naturals
All are highly visible on the GIA report and cover its table and pavilion.
Their location means you couldn’t cover them up with the setting, so any dark or large inclusions could be visible to the naked eye.
In rare cases, a diamond could earn an SI1 clarity grade because of one or two inclusions.
If they’re large enough or have an adverse effect on its durability, it could be a single twinning wisp or feather that brings it from flawless to SI1.
But in most cases, you’ll be dealing with three to five types of inclusions for SI1 clarity and two or three for VS1 diamonds.
2. Inclusion in SI1 Diamonds are More Impactful
One of the criteria gemologists use in assigning clarity grades is how much the inclusions affect the performance of a diamond, which generally fall into three categories:
Most buyers want a diamond that displays fire and brilliance and doesn’t have visible flaws or durability issues.
The higher a diamond lands on the clarity scale, the more likely it is to reach this ideal standard.
VS1 diamonds meet this criteria more than SI1 diamonds.
Inclusions that result in a VS1 grade often have no impact on its appearance and have a minimal effect on durability and brilliance.
First, you only have to worry about the visibility of inclusions in a VS1 diamond if it’s over two carats. The large surface area on these diamonds means small blemishes are more likely to be noticeable.
Any weight less than two carats means it’s likely eye-clean.
Take this VS1 princess cut as an example.
The GIA report shows the presence of five types of clarity characteristics, but they have no obvious impact on its appearance.
These inclusions also don’t result in durability issues. Diamonds with large inclusions, or ones near vulnerable areas like an extremely thin girdle, may result in a chip, but VS1 diamonds don’t fall into that category.
Large feathers or cavities cause the most concern because they represent weak points in its structure.
Although inclusions affect how light can enter and exit a diamond, the most important quality to enhance the brilliance of a diamond is cut.
An excellent cut diamond can exhibit sparkle even with the small inclusions in a VS1 diamond.
These qualities are similar in an SI1 diamond but to a lesser extent.
The higher number of inclusions, or their size and position, means they will have more of an effect on appearance, durability, and brilliance but less than you would experience with an SI2 or I1 diamond.
3. VS1 Diamonds are More Expensive
Buyers are willing to pay premiums for diamonds that score higher across the four Cs of color, carat, cut, and clarity.
VS1 diamonds have better clarity than ones graded SI1, so they’re more expensive.
The best way to understand how clarity affects the price of a diamond is to compare ones that have similar grades across all other qualities.
We examined prices for round cut diamonds from James Allen with the following qualities:
- Carat weight: 1.05
- Cut: Excellent
- Color: H
For diamonds with a VS1 clarity grade, the average price is $7,307, with a range of $6,300-$8,120.
For ones graded SI1, the average cost is $5,993, and the range is $5,070-$6,900.
That’s an 18 percent lower cost for an SI1 versus VS1 diamond.
To the naked eye, most of those diamonds will look identical, but there’s a higher charge for the ones with fewer inclusions.
That’s why we recommend choosing a diamond that’s eye-clean while avoiding the premiums for ones with very few inclusions.
SI1 and VS1 diamonds fall into that category.
As a general rule, you can expect the price of a diamond to increase 10-20 percent for every step up the clarity scale.
The difference is more pronounced when moving from one category to the next, like SI and to VS or internally flawless to flawless.
Are There any Similarities Between Them?
There are also similarities between SI1 and VS1 diamonds.
Both grades often mean the diamond is eye-clean, which allows you to buy the best value.
Most buyers aren’t concerned about whether inclusions are visible with a jeweler’s loupe or if the diamond earned one clarity grade or another.
Instead, they want a diamond that looks flawless to the naked eye.
By choosing an SI1 or VS1 diamond, you can avoid the price premium charged for VVS or flawless diamonds but have one that looks identical.
In fact, for diamonds less than 1.5 carats, we recommend starting your search with SI1 clarity for its value.
View the diamond in person or through high-resolution images to ensure the inclusions are invisible, and you can put that savings toward the setting or other qualities about the diamond.
VS1 and SI1 diamonds are also common for engagement rings. The lack of visible inclusions means it can serve as the center stone on top of your setting.
This is in contrast to an I3 diamond, which has inclusions that are obvious to the naked eye.
Any diamond graded below SI1 deserves special attention before choosing it as your engagement ring diamond because you don’t want noticeable inclusions on the most prominent part of the ring.
Is an SI1 or VS1 Diamond Right For You?
If you’re searching for a diamond, you should compare SI1 versus VS1 diamonds as potential picks. Both can serve as the center diamond on an engagement ring as an eye-clean, sparkling gem.
Here are some tips to help you decide.
You should choose an SI1 diamond if:
- You’re looking for the most affordable option that still has the potential to be eye-clean
- You want to put your savings from the center diamond toward other qualities about the ring such as its carat weight or setting
- You’ve examined the diamond in person or through high-resolution images
Consider a VS1 diamond if:
- You want more confidence the inclusions are only visible with magnification
- You’re willing to pay a premium compared to diamonds with lower clarity grades
- The diamond weighs more than two carats
Explore SI1 and VS1 diamonds at online and in-person vendors. By pairing them with different settings, you’ll find the right combination for your diamond ring.