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SI1 vs. VS1 Clarity Diamonds (Differences)

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SI1 vs VS1 Clarity

Clarity is one of the many factors to consider in search of the perfect diamond for you.

It refers to the presence of inclusions, or blemishes, in the diamond and how they affect its appearance, durability, and brilliance.

Institutions like the the Gemological Institute of America (GIA) assign a clarity grade to diamonds based on its internal and external flaws.

On one end of the scale is flawless, where inclusions aren’t visible with 10x magnification, and on the other end is I3, which indicates it has significant inclusions.

Let’s compare SI1 versus VS1 diamonds, including an overview of these grades, their differences and similarities, and how to know which clarity grade is right for you.

What is an SI1 Diamond?

SI1 Diamond

An SI1 (slightly included) diamond has inclusions visible with a standard jeweler’s loupe at 10x magnification. 

On the 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, feathers, or indented naturals.

Instead, the gemologist combines a number of factors to determine the overall grade. These include:

  • The size of the inclusions
  • Their position
  • Visibility
  • How they affect light performance

The diamond will be 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 earned an SI1 clarity grade. 

SI1 Clarity Diamond

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. This 1.05 carat diamond from Blue Nile has crystals, twinning wisps, and needles. 

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 or the Gem Certification and Assurance Lab, allows you to know 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. 

VS1 Diamond Ring

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.

Instead, 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. 

VS1 clarity diamond

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.

What are the Differences Between SI1 and VS1 Diamonds?

The difference between SI1 and VS1 diamonds is the extent to which the inclusions affect its brilliance, visible appearance, and durability. 

While they may have specific inclusions in common, SI1 diamonds have more impactful flaws compared to VS1 diamonds.

If you’re comparing SI1 versus VS1 diamonds, here are three differences you should know.

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 of inclusions will likely prevent the diamond from reaching the very slightly included status.

Let’s compare two cushion cut diamonds from Blue Nile. 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. 

GIA Report for VS1 Diamond

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:

  • Crystals
  • Feathers
  • Cavities
  • Needles
  • 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. 

Diamond with SI1 Clarity Grade

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.

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:

  • Appearance
  • Durability
  • Brilliance

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 do minimal damage to its 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.

The 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.

Girdle of Diamond

Although inclusions affect how light can enter and exit a diamond, the most important quality to enhance the brilliance of a diamond is cut. 

A very good or 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.

VS1 Diamonds are More Expensive

Buyers are willing to pay a premium 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.

VS1 Clarity Diamond Prices

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.

Are There any Similarities?

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. 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 SI1 clarity for its value. 

View the diamond in person or through high-resolution images online to ensure the inclusions aren’t visible, 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 a potential pick. Both can serve as the center diamond on an engagement ring as an eye-clean, sparkling gem.

Not all diamonds with these clarity grades are created equal, so you should know the specific inclusions and their relative size in any diamond you’re considering.

If your diamond is two carats or larger, we recommend beginning your search with VS2 or VS1 diamonds.

If it weighs less than that, you can often find an SI1 diamond that’s eye-clean.

By comparing several diamonds with varying clarity grades, you’ll find the right one for you.

Devon Tyler

Devon Tyler

Devon Tyler is the founder of TeachJewelry.com.

He earned an Applied Jewelry Professional Diploma from the Gemological Institute of America and now brings you essential information about diamonds, settings, and more.

Devon has consulted with leading jewelry brands, and his work has been cited in Diamond Nexus and other industry publications.

He's also a member of the International Gem Society.

Devon enjoys discussing jewelry with readers, so contact him with any questions at tyler.devon@teachjewelry.com.

Learn More About Devon

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