Diamond grading helps standardize and set the value and price of all diamonds. Labs use trained staff known as gemologists and special equipment to accurately identify the characteristics and attributes of every diamond. A diamond's sparkle is represented by its graded components such as clarity.
Clarity is graded face up under 10x magnification with a tool called a loupe or diamond microscope. This is used to identify the tiny imperfections known as clarity inclusions. When these inclusions, given their type, size, number and location, are noticeable, that are graded as SI or slightly included.
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|FL||Flawless: No inclusions under 10x. A stone that is completely flawless. This is an extremely rare find.|
|IF||Internally Flawless: No internal imperfections. A stone that has no internal flaws at all but does have surface flaws. Also, an extremely rare find.|
|VVS1-VVS2||Very Very Slightly Included: A stone with very minute internal inclusions that are extremely difficult to see under a 10X magnification.|
|VS1-VS2||Very Slightly Included: A stone with very minor internal inclusions that range from difficult to somehwat easy see under a 10X magnification.|
|SI1-SI2||Slightly Included: A stone that has imperfections visible under X10 magnification and may be visible with the unaided eye.|
|I1-I3||Included: A stone that has significant inclusions most often visible with the naked eye. Inclusions of this level drastically bring down the diamonds value.|
SI means the diamond has small inclusions that are noticeable with 10x magnification and may possibly be seen without any magnification, especially if they are larger or in the center of the diamond where facets aren't helping to hide the inclusions. SI has a range that consists of SI1 and SI2 (slightly included 1 and slightly included 2). SI1 means smaller inclusions in number, size and location than SI2. The size of the inclusions tends to be medium in nature and the location can be anywhere (center under the table or on the sides near the diamond girdle). SI diamonds tend to have more centered inclusions because they are noticeable. The number of SI2 and SI1 inclusions can vary. It can be a single inclusion or several at a time. Typically, you can expect that there will be 1 grade setting inclusion rather than many smaller ones.
Common SI1 inclusions are crystal (white or black), feather, indented natural, knot, needle, cavity, chip, clouds, twinning wisps. Common SI2 inclusions are crystal (white or black), feather, indented natural, knot, needle and cloud, cavity, chip, twinning wisps as well. Because SI diamonds are below VS2 (very, slightly included 2), they are for the more budget conscious purchaser and offer a very good value. Less than 50% of all of the world's gem quality diamonds are in this range. SI diamonds can be 10%-20% less expensive than a VS diamond. They are very much in demand, especially SI1, because the inclusions aren't outwardly obvious. They allow consumers to have other Cs such as carat or color optimized.
Both SI2 and SI1 clarity diamonds have inclusions that you might be able to see with the naked eye, some big, some small and can be seen on the center or sides of the stone near the girdle. The biggest differences in the SI2 vs SI1 debate are the number and type of inclusions they have.
SI1 diamonds tend to have fewer inclusions than SI2, as few as one inclusion, to several in the same diamond. The inclusions tend to be smaller and can range from crystals to feathers, knots, needles, cavities, chips, clouds, twinning wisps or indented naturals. SI2 diamonds, on the other hand, will have the same types of inclusions as SI1 diamonds, just more of them. They tend to be larger, too.
As for their looks? Well, that depends on the actual stone. As you can see, there isn't always a huge difference in appearance when it comes to SI2 vs SI1 diamonds. One might appear foggier or have a less-than-perfect appearance when compared to the other, but the typical ring admirer probably won't be able to tell the difference in the shine between the two.
SI diamonds are very popular because even though they may have clarity characteristics that are eye visible, it's not terribly distracting from sparkle. To the naked eye, diamond sparkle is slightly impacted and light performance is still quite high. Typically, only when the diamond grade is set by clouds or a single large inclusion, it can have a distracting impact. There are typically not structural problems that would cause chips or cracks in the diamond when set in jewellery, even if the inclusions are closer to the girdle. It is still advised that SI diamonds are set carefully be very experienced setters. While it's not perfect, it's certainly very respectable and valuable to have a SI diamond.
Most often, no one will come close enough to even see or identify the inclusions. The value of SI diamonds will appreciate over time, like most other high quality diamonds. This is mainly due to their rarity and increase in diamond demand. Preference has generally shifted to quality over time, meaning consumers prefer quality over plain carat weight. We generally recommend not going below SI clarity, especially in larger diamonds as the imperfections get larger and are more like to be seen. In smaller carat diamonds (below 0.50 ct), SI inclusions will not be eye visible.
You can buy SI quality diamonds from a variety of reputable jewellers; however, the types of SI diamonds may differ for each jeweller. This is particularly important as the imperfections may be better or worse, depending on the jeweller's inventory. Start by viewing jeweller's online pair the clarity with the other diamond 4Cs to identify if SI is the right clarity range for you given your price range and budget. Like everything else, clarity is something you should balance and determine how important it is for you.
The biggest upside to an SI diamond is the price. SI1 diamonds are just a grade below a Very Slightly Included 2 diamond, meaning they're very similar, but with very different prices. Typically, an SI diamond will save you anywhere from 10 to 20 percent over a VS diamond. You will also see a price difference when you compare an SI2 vs SI1 diamond, but the actual difference depends on the actual stone itself.
Simply put, SI clarity diamonds should be evaluated on a case by case basis for your diamond engagement ring. We advise customers against buying, some SI diamonds that are not ideal for brilliance.
If you want to invest in SI diamond, it's best to work with a gemologist who can help you find the best stone with the fewest inclusions. An expert gemologist can also help you pick a diamond engagement ring setting that'll help mask any inclusions that take away from the beauty of your stone.