Buying a diamond is all about making small tradeoffs to help you land the best looking diamond for your budget. Given the choice, everyone would prefer to buy a huge, high quality diamond at a low price. Unfortunately the laws of economics work in such a way that the better a diamond is, the more it will cost. Buying an SI1 clarity or VS2 clarity diamond is a great way to help you stretch your budget while still getting a beautiful stone. On the GIA’s diamond grading scale an SI1 clarity grade is one level worse than a VS2 clarity grade, but an SI1 diamond may not always look worse than a VS2 diamond - it all depends on the types of inclusions and their locations.
Clarity grades are used to describe how many imperfections exist within a diamond. These imperfections are typically caused by small crystals that were trapped within the diamond while it was forming. VS2 clarity means that the diamond has small inclusions which are not visible to the naked eye, but that could be seen under 10x magnification by a trained eye. These inclusions are considered very minor and shouldn't affect the diamond’s visual appearance. SI1 clarity indicates that a diamond has some small inclusions that are more easily noticeable under 10x magnification, but are difficult or impossible to see with the naked eye.
These imperfections should be pretty easy to spot if you see a magnified video of the diamond or view it through a jeweler’s loupe (a tiny magnifying glass). Keep in mind that when you're looking at diamond images online they are often enlarged by 20x or even more - the inclusions you see at this level of magnification won't necessarily be visible in person. Pro tip: shrink diamond images down to the size of your pinky finger nail on your computer monitor or smart phone to get a more realistic look.
Eye clean is the term used to describe a diamond that appears flawless to the unaided human eye, but that may contain imperfections that are visible using magnification such as a jeweler’s loupe. Some SI1 diamonds have imperfections that are visible to the naked eye and are thus less desirable than other SI1 diamonds that do not have visible inclusions. Often times an eye clean SI1 diamond will cost nearly as much as a VS2 diamond and consumers will still buy them because buyers are under the impression that the diamond’s lower clarity grade always means a cheaper price.
When it comes to eye clean, you can work to find a good SI1 or SI2 eye clean diamond if you dive deep into images and videos. In my opinion, you should focus on VS2 or better for two reasons. #1 It's much less of a treasure hunt searching for an eye clean VS2 - the vast majority of VS2's should be eye clean. #2 Even when you find a good, eye clean SI1 - it's likely to be priced comparably to a VS2 diamond or else not at much of a discount. In order to maximize your diamond search on any site I recommend that you do something similar to the following which is taken from a real question asked on reddit.
Set a color range of J - D, clarity VS2 - IF or FL (whichever is available as the max), excellent only for cut/polish/symmetry, GIA only as the grading agency, none - medium fluorescence (this can save you a lot and also look great on a J or I color diamond), carat range from 1.90 to max, and set your budget from $0 - $15,000. By doing this you leave open the possibility of finding underpriced VVS2 clarity diamonds etc. - most people aren't actively searching for these diamonds and they pop up as great values. For example - the type of person looking for J color often isn't looking for VS1 or VVS2 clarity and that lack of demand means that these diamonds can end up pricing much lower than they normally would. On cut - our site takes things to the next level and allows users to filter within excellent cut quality to narrow it even further. If you use StoneAlgo I'd recommend all of these setting plus filtering for 8.4 - 10 on our cut quality scale which equates to the top 50% of GIA excellent cut diamonds. In order of importance I personally try to stay within these minimums but maximize Cut, Carat, Color/Clarity in that order. Here's a search that incorporates the filters discussed above if that helps: StoneAlgo Custom Search.
Most jewelers will recommend you purchase an SI1 or VS2 clarity grade because it allows you to spend more money in other areas, such as getting a better color grade or a larger carat weight. StoneAlgo recommends you explore the best available prices for VS2 diamonds before looking at SI1 diamonds because VS2 diamonds should be eye clean while SI1 diamonds take more work to evaluate. However, it’s important to view images and videos of any diamond you plan to buy online before you purchase. Oftentimes these videos and images are far superior to viewing the diamond through a jeweler’s loupe in terms of seeing the imperfections easily.
You should not only consider the types of inclusions but also the inclusions that are listed on the certificate as "not shown" - if these inclusions include clouds then you should be wary, especially with SI1 or worse clarity. The placement of the inclusions relative to the flat top of the diamond is also an important point of consideration. Ideally, any inclusions should not be visible through this flat top area - this can create even more room for concern in fancy cut shapes that have larger tables. If you want to see the impact and various ways to save money when buying an engagement ring, check out our post on how to maximize your engagement ring purchase.
When a jeweler sets a diamond in a setting he can choose which parts of the diamond are covered by the prongs on the setting that hold the stone in place. Certain inclusions that could cause a diamond to be graded as SI1 or SI2 (one grade worse than SI1) could be easily covered if they appear near the outer edge of the diamond where a prong can be positioned over the visible inclusion. Other types of inclusions, such as thin, white, hair-like inclusions are less easily discerned without the aid of a microscope, especially if they are near the bottom of the diamond or off to the side.
Let’s start with a real life example to see the differences in price by looking at two 1.5 carat, I color, triple excellent, GIA certified round diamonds that feature real images and are available from StoneAlgo’s top online jewelers. On the date this article was written, the lowest priced VS2 version was $7,639 while the lowest priced SI1 version was $7,266. The most expensive VS2 version was priced at $11,108 while the most expensive SI1 version was actually more expensive at $11,250. As you can see, the price ranges for 1 carat, I color diamonds of SI1 and VS2 clarity are very similar. The difference in price between the least expensive SI1 and VS2 diamonds was only 5.1%.
Let’s see what that 5% savings looks like. In the video below you can see a comparison of these two diamonds, the major difference being the small inclusion in the top center of the SI1 version. You may not notice it, but the VS2 version has a small inclusion in a similar location. Check out the video to see the difference between these inclusions. Remember, when a diamond is placed in a setting the only part of the diamond visible to the naked eye will be the top of the stone.
Admittedly, both of these diamonds have inclusions in the top center of the stone which is considered the worst position for an inclusion to appear. However, the impact of those inclusions on the diamond’s visual appearance is over emphasized by the scale to which these images and videos have been magnified. If you shrink the video down to about half the width of a penny you will get a better idea for how the stone looks without the aid of magnification.