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In many cases, diamonds represent a very solid investment, not only in terms of something that won’t diminish in value, but also in terms of something that won’t diminish in quality or beauty. However, this is only guaranteed when you’ve found the right diamond — and the right diamond for you could be an SI1 Clarity Diamond. 

What Is A SI1 Clarity Diamond?

On the universally recognized diamond grading scale, SI1 sits at the top of the ‘Slightly Included’ tier. This means that inclusions and blemishes can be found by a jeweler using a loupe at 10x magnification. However, in most cases, SI1 inclusions can’t be seen by the naked eye.  

In other SI1 Clarity Diamonds, these flaws can be seen, even without magnification. With some diamonds, the size, location, cut, and color of the diamond will make it either harder or easier to notice these inclusions. These all work to lessen or increase the impact on a diamond’s overall clarity.

Clarity is a term used in the diamond industry to refer to the visual appearance of the diamond, such as the presence of blemishes and inclusions. The grade ‘SI1’ is part of a wider range of diamond grading determined by the Gemological Institute of America (GIA). This divides eleven grades into six categories:

  • Flawless (FL)
  • Internally Flawless (IF)
  • Very, Very Slightly Included (VVS) — VVS is divided into two grades, VVS2 and VVS2
  • Very Slightly Included (VS) – VS is also divided into two grades, VS1 and VS2
  • Slightly Included (SI) – SI is divided into SI1 and SI2
  • Included (I) – Included divides into I1, I2, and I3

Why Choose A SI1 Clarity Diamond?

SI1 Clarity Diamonds have the potential for being great value for money, but this depends on the features of the diamond itself, mainly the carat weight, the cut of the diamond, and the number, size, and location of inclusions. 

The main reason you should choose an SI1 Clarity Diamond is, if they don’t contain any visible inclusions and the quality of the cut is high, they can be just as impactful and visually beautiful as a VS1 or a Flawless diamond. 

However, this will only happen if the SI1 Clarity Diamond has been shown to be ‘eye-clean’, meaning there are no visible imperfections. Essentially, you get a cheaper diamond that looks just as good as diamonds that come at a higher grade and higher cost. 

The Cost of A SI1 Clarity Diamond

Because SI1 diamonds are at a lower grade than F, VS1, and VS2, they will naturally have a smaller price tag. 

For example, if you look at this 0.802 ct F VS1 A CUT ABOVE® Hearts and Arrows Diamond, by Whiteflash, you’ll see a stunning, eye-clean diamond that truly dazzles. Its price is set at $5,163.

Compare this with another diamond by Whiteflash, this 0.801 ct F SI1 A CUT ABOVE® Hearts and Arrows Diamond. It is the same color, the same carat weight, and is also eye-clean. However, it costs $3,989.00, meaning this diamond is 22% cheaper. 

0.801 ct F SI1 A CUT ABOVE® Hearts and Arrows Super Ideal Round Cut Loose Diamond

Image Courtesy Whiteflash

However, finding an eye-clean SI1 can be difficult. Due to their lower grading, many contain imperfections. Now, these imperfections are usually slight and won’t be seen unless very closely inspected. 

Should You Buy A SI1 Clarity Diamond?

For diamond lovers, clarity grading is an important way to determine the overall quality of a diamond, but it’s not the be-all and end-all of whether a diamond should be chosen. If you’ve really fallen in love with a particular diamond, that’s the most important thing. 

It is essential that diamond buyers know that clarity grading is determined by the features of inclusions — their size, number, harshness, and so on, in relation to the size of a diamond. However, that grading doesn’t explicitly state whether inclusions will be visible to the naked eye. When a diamond with a high-quality cut is shining on someone’s finger, no one, not even an expert, will be able to spot a blemish. 

But be prepared to notice inclusions as you choose an SI1 Clarity diamond. A good rule of thumb to work from is; The bigger the diamond, the more likely you are to notice inclusions. 

Working With Clarity Plots

When you purchase from a trusted and experienced diamond retailer, such as Whiteflash, Blue Nile, or James Allen, they will provide you with certification to show you the data and details of the diamond you’re considering. 

They will provide you with what is known as a Clarity Plot, which maps the inclusions within a diamond, detailing their position, size, and type. It will be natural for an SI1 Clarity Diamond to have these inclusions. 

Clarity plots are good references for the discerning buyer. First of all, they show that a gemstone has undergone modern analysis to determine grade, meaning you can be reassured within your purchase. Secondly, they help you narrow down the diamond you want. 

If a clarity plot has no information present, it usually means that there is a hidden flaw that is affecting the clarity grading. Always consult these before making a purchase to see what potential inclusions a diamond may contain and whether it’s worth the money you will spend. 

How to Choose a SI1 Clarity Diamond

Choosing a diamond is usually dictated by the Four Cs; Carat, Cut, Clarity, and Color. Now, as we’re talking about SI1 Clarity Diamonds, that C has already been decided. However, remember to weigh up the others:


When it comes to diamonds, cut is the most important factor for determining quality, as it actually has the most impact on the overall quality and performance of the diamond.

When cut, a diamond is essentially an item containing a number of tiny mirrors, each taking in and bouncing light in multiple directions. For the best light performance, a diamond should be cut with absolute precision, which makes for better light performance. The American Gem Society provides a grading scale for diamond cuts:

  • 0 – Ideal
  • 1 – Excellent
  • 2 – Very Good
  • 3, 4 – Good
  • 5, 6, 7 – Fair
  • 8, 9, 10 – Poor

You can find more information about diamond cutting on our diamond cut education page.


While, in general, the standard for an excellent diamond is colorless, color is really a subjective feature of a diamond. Many retailers and buyers want colorless, while others can be particularly interested in colored diamonds. 

For example, if a diamond is colored with a very saturated yellow color, it’s known as either a ‘fancy yellow diamond’ or a ‘canary diamond’, which is quite popular in some circles. 

If you’re looking for a colorless SI1 Clarity Diamond, choose a diamond that sits within the colorless ‘D-F’ bracket. 


For the uninitiated, carat represents the weight of the diamond. Usually, the higher the carat, the more expensive the diamond, as higher carat diamonds are rarer than their smaller counterparts. 

One carat diamonds set the industry standard, being the most popular weight. With many retailers, you can search for diamonds through weight alone, with many offering their weighings within three decimal points. 

However, like color, diamond carat is subjective. 

SI1 Clarity Diamonds: Our Final Recommendations

In our opinion, while SI1 are not the highest grade of diamond, they’re still well worth the investment. However, there are a number of things you should keep in mind:

  • For SI1 Clarity Diamonds, choose an ideal round brilliant cut. These types of cut are excellent at concealing inclusions or making them less noticeable due to the facet patterning in this design, which greatly enhances light performance.
  • We can’t stress the importance of an eye-clean diamond enough. We will always recommend ensuring the first quality a diamond has before purchasing is being eye-clean. It’s in your best interest to find the most affordable eye-clean diamond within the clarity grade you’re targeting, so you’re getting the most value for money. 
  • Remember that not all SI1 Clarity Diamonds are the same. This applies to most diamond grades, where simply because two diamonds are in the same grading, doesn’t mean they will be alike at all. Take this into account especially if you’re looking for more than one diamond. 
  • Purchase from diamond retailers who keep their diamonds in stock. This means that diamonds can be pulled for analysis or viewing upon request, rather than buying from virtual sellers who may have not even seen the diamonds they’re selling. Also, offerings such as high-res diamond imaging and 360 HD videos are vital for making a good assessment. 

Overall, we would argue that an SI1 Clarity Diamond is a fantastic way of getting a good quality diamond for an incredibly affordable price, which is perfect for those who wish to stay within a modest budget.

Our final recommendation is to always work with a trusted and experienced diamond retailer, such as Blue Nile, James Allen or Whiteflash. Make sure the vendor you select has gemological experts who use the latest technology to discover the intricate qualities of a diamond, helping you to make the right choice in your diamond purchase, every single time. In addition, please get in touch with me directly for any help selecting a diamond.

Richard Jenkins, The Diamond Guru

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