February 15

What Does SI Diamond Mean? | A Full Guide to This Clarity Grade!


Author: David Kopelman

Key Takeaways

  • SI diamonds mean the stones are Slightly Included, and any inclusions are easy to see under magnification.
  • Evaluating the clarity of SI diamonds involves determining the size, number, nature, and location of inclusions present.
  • SI diamonds come in towards the lower end of the grading scale for clarity, but it doesn’t mean they are lower clarity grade diamonds.
  • The Gemological Institute of America (GIA) ranks diamonds on a clarity scale from best to worst.

This article discusses what SI diamond means and the different SI categories. We also discuss the role of grade clarity in grouping diamonds. Let’s dive in!

What Does SI Diamond Mean? Every Key Detail to Know

Diamond clarity grade SI stands for Slightly Included (SI). SI diamonds have obvious inclusions that are easy to identify with magnification.

When gemologists determine the clarity of diamonds, they often use a jeweler’s loupe with 10x magnification to scan back and forth. Thanks to the diamond clarity grades, it’s easy to look at aspects that affect the free passage of light through the stone.

a woman observing a diamond

These inclusions and imperfections range from Included (I) to flawless (FL). To obtain a grading of SI, the diamond you buy should have noticeable inclusions that can be easily seen under 10x magnification.

These tiny inclusions are visible to the naked eye without magnification. The common inclusions in SI diamonds include:

  • Knots
  • Clouds
  • Needles
  • Indented naturals
  • Crystals

Tiny surface-reaching inclusions include cavities, feathers, and chips.

When evaluating diamonds, it is vital to check the clarity grade. The SI diamond clarity tells you the harshness and size of a blemish or inclusion in relation to the type of diamond.

SI clarity grade diamonds may have visible inclusions which can be considered insignificant even from a short distance. As a result, these diamonds appear flawless and beautiful.

The grade SI is the lowest type on the GIA diamond clarity scale (Gemological Institute of America). Slightly Included diamonds are further divided into SI1 and SI2.

graphic scale of diamond clarity

What Are SI, SI1, and SI2 Diamonds? How Are They Different?

SI clarity diamonds mean their inclusions are easy to find with a standard jeweler’s loupe at 10x magnification. SI1 is considered to be of a higher clarity grade than the SI2 diamond.

The main difference between SI1 and SI2 diamond clarity lies in the visibility of the inclusions. You’re more likely to notice these minor inclusions in SI2 diamonds than those grades in SI1.

Further, inclusions in SI2 diamonds are, on average, bigger and more numerous. The visibility will also depend on the location of the blemish in the diamonds and their color.

Choosing between SI1 and SI2 clarity shouldn't be daunting if you know where to start. The good thing is that it all comes down to the tradeoff between the diamond quality and price.

SI2 diamonds are much cheaper, but SI1 are cleaner on average, with some having inclusions visible to the naked eye.

You’ll also find SI2 stones that look reasonably clean. Each diamond is unique, so you should use clarity grades to choose the right stones.

When looking for a diamond engagement ring, it’s best to opt for a type that doesn’t have ugly blemishes in the middle.

However, if you have an SI1 and SI2 diamond with visible inclusions, it doesn’t mean you can’t use them. Such stones are an excellent choice to fit on diamond studs and pendants, especially if the diamond jewelry can easily hide any inclusions. Hence, when choosing SI1 and SI2 diamonds, it’s imperative to consider their visible properties.

a pair of gold diamond studs

SI Diamonds Buying Guide

If you’re planning on buying diamonds, there are priorities to keep in mind. Among these are the four C’s (Cut, Color, Clarity, and Carat weight) that define the quality of a diamond.

To determine the value of SI diamonds, these are the aspects that will help pick the best SI diamonds:

Types of Clarity Features

The value of the two diamonds you choose may vary significantly by checking their clarity characteristics. These clarity features include:

  • Twinning wisps
  • Feathers
  • Cloudy formation
  • Pinpricks
  • Bearding
  • Cavity
  • Needle
heart shaped diamond pendant on the dark surface

Reading a Clarity Chart 

Taking a look at the SI diamond's grading report can help pick the right stones. A clarity chart will help choose a beautiful diamond by indicating the type of clarity features and their location. You'll easily give each diamond a clarity grade within a given scale.

Clarity and Durability 

The diamond industry may consider these stones as the hardest minerals. However, they can still break depending on their clarity features.

Any inclusion, small or large, is a vulnerability to the diamond's density and strength. Imperfections close to the diamond's surface can result in a diamond breakage.

Durability and Diamond Shape

Put a lot of concern on the corners of diamond shapes. Ensure there are no large inclusions in these areas.

A marquise cut diamond, trillion, heart or pear shape may have prongs that pressure the stone. With any inclusions in the prongs, the diamond is vulnerable to breaking.


SI diamonds are affordable compared to VS diamonds and especially to VVS1 diamonds. However, you should not sacrifice their eye cleanliness to save on price.

There is a huge demand for diamonds with few blemishes or flaws. The cost of diamonds also increases because diamonds with minimal imperfections are rare.

SI diamonds are a great choice if you are on a tight budget. They have a lower price range compared to Very Slightly Included diamonds. They are also almost flawless to the naked eye.

The bigger the SI diamond, the more you are likely to pay. A 1-carat D-color round diamond will measure 6.5mm in width and may cost $5,000 to $10,000.

an isolated diamond ring


What Are SI Diamonds Worth?

Strictly Included diamonds are worth the amount you spend. The value of the SI diamonds you pick will depend on carat size, cut, and color. They can be 40-50% less costly than other flawless diamonds.

Which Diamond Is Better VS Or SI?

Good diamond grades fall between VS and SI, but you must settle for the best. VS diamonds look magnificent even under 10x magnification. On the other hand, SI diamonds are a good deal but have noticeable inclusions that affect their appearance and durability. Hence, VS diamonds are a top pick for their beauty and affordability.

Is an SI Clarity Diamond a Good Deal?

Yes, SI clarity diamond is a good deal because it's affordable. You can also go for an eye-clean SI1 diamond which is a much better choice. With an SI clarity diamond, you will surely get value for money.

What Is The Best Clarity For A Diamond Engagement Ring?

It all depends on preference. Most people think that a diamond with no flaws or flaws on the inside is better than one with flaws on the outside. But that’s not always so. That is because perfect diamonds, both externally and inside, are rare and, therefore, quite expensive. A higher-carat stone of unusual cut will cost substantially more than a similar stone with even minute imperfections.

If you are shopping for an engagement ring on a limited budget and the clarity of the stone is not your top concern, your best bet is to search for diamonds in the Slightly Included (SI1) category.

About the Author:

David Kopelman

In every article I write, I share my experience as a GIA Graduated Gemologist so that you learn everything about diamonds and other precious stones.

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