The GIA clarity grades are used to rate how “included” a diamond is, a measure of how many imperfections exist inside the diamond and blemishes on the surface of the stone. The seventh highest clarity grade is SI1 which stands for Slightly Included 1, one grade lower than VS2 (Very Slightly Included 2) and one grade better than SI2. While these diamonds are not considered “flawless”, the inclusions present within these diamonds can be small enough that they will not be visible to the naked eye - but this often depends on which types of inclusions they are and where they are located. For example, an inclusion that appears in the middle/top of the diamond will be much more visible to the naked than an inclusion that appears off to the side or lower down. Often times, the price of a diamond will vary depending on the types and locations of that diamonds inclusions. SI1 diamonds are not always “eye clean” (a term meaning that no inclusions are visible to the naked eye), but buyers should always view the inclusions present in their diamonds to ensure they are not in an undesirable location or, if they are, that they are not large enough to be seen by the unaided eye.
SI1 diamonds are still within the range that jewelers typically recommend to their clients (basically grades from SI1 to VS1), as the imperfections can be too small to be seen by the human eye. StoneAlgo typically recommends that you target a VS2 clarity diamond to begin with when buying a stone and make sure to view images and videos of any diamond you plan on purchasing. Even if an online jeweler does not have images of a diamond listed on its site, you can contact their customer service to request that images and videos be e-mailed to you for evaluation. Also, you should be aware that different shapes of diamond hide inclusions differently. For example, a round shape diamond will hide inclusions more easily than an equivalent quality stone with a larger flat surface area (such as princess or cushion cut).
Diamond buying is all about making small tradeoffs to maximize the criteria you care most about, whether that means getting the largest diamond or the highest quality stone (or somewhere in between) is a matter of preference that every buyer must determine. One thing you should know before you begin investigating tradeoffs is that going one grade lower in clarity will save you less than going one grade lower in color. It’s also important to consider that above a certain point, no one will be able to see the difference between a perfect diamond and a very good diamond unless they have a magnifying glass or a diamond of significantly higher quality to compare it to. We typically recommend you begin your search at I color, VS2 clarity and always see what the diamond market looks like for better or worse colors and clarities while requesting videos and images of every diamond you are interested in buying.
There are a lot of moving parts but generally speaking we try to maximize carat size for our given budget by sticking to the lower end of the color ranges we specified and searching for VS2 or better diamonds. SI1 diamonds are great if they’re eye clean, but they are a pain to find and often end up costing just as much as a VS2 diamond would. If you need one-on-one advice, we offer free support to all our users – simply drop us a line at firstname.lastname@example.org