SI1, SI2 and SI3
SI is the abbreviation for "small inclusions" which now become "easy" (SI1), very easy (SI2), and almost obvious (SI3) to see under 10x magnification. In some SI's the inclusions can be seen with the unaided eye.
While you can pretty much expect what to see under a scope when you look at stones that are VVS and VS (really tiny imperfections), the SI clarity grade can range from quite a spectrum as there is more to see. The SI1 grade is still a pretty descent looking stone from the perspective of "under the scope", but when you get into the grade of SI2 and then even SI3... well let me say this: Not all SI2's are created equal. Diamonds become less rare as we move down the clarity scale. This clarity grade is probably the most popular (in brilliant cuts) for 2 reasons:
When the expression "eye clean" is used, this means observing the diamond "face up" as it is mounted in a ring and viewed from roughly half an arm's length in distance. If you take an SI clarity (and even some VS's) grade diamond and turn it face down, it is possible to see the imperfections (and/or even reflections of the imperfections) with the unaided eye. There's nothing wrong with observing a diamond upside down when you're inspecting it, but it could be an inaccurate representation of what the clarity really is.
Let's see some examples:
Here is a nice SI1 with a feather in the 4:00 position and also in the 9:00 position. These are completely invisible to the unaided eye.
With each of our diamonds we also generally include additional graphics pointing out where the primary grading inclusions are, as in this example below of the same stone.
Here is another SI1 below. Also completely eye clean.
Here is an example of an SI2.
In the GIA's official definition of SI it states: "In some SI's inclusions can be seen with the unaided eye." Let me say this about the lower end SI's (like lower end SI2 and SI3): First of all, you are going to be observing what these stones look like under the scope here at "The Ultimate Diamond Information Site", and you are going to be seeing examples of SI2's that are completely eye clean and some that are not. As I progress in developing this site I will be putting up more examples. In the SI2 clarity grade, if you have eyes like a hawk and after you have examined the stone under the microscope as you will be doing here, it may be possible to see it with your human eye. If you do purchase an SI2 or SI3 and after viewing the diamond under a scope you can make out the inclusions under certain lighting or conditions, don't have a cow. When a stone is termed "eye-clean", this generally means that as the casual observer looks at the stone (such as friends, relatives, etc.), there will be no large inclusions jumping out that are obvious.
A word about SI3. This clarity grade has already been in use for a very long time. It wasn't until about 1993 or 1994 that wholesale diamond reports started listing a trading price for this clarity grade. There never used to be an official grading of SI3. You see, there are diamonds on the market that have more inclusions than what an SI2 should have, but aren't so obvious that they would be graded Imperfect. An SI3 is a stone that would be considered a low-end SI2 or a high-end I1. Neither the Gemological Institute of America (GIA) nor the AGS (American Gemological Society) at this point recognizes this clarity grade, and they will grade a stone as either an SI2 or an I1. The world-renown European Gem Lab does recognize this clarity grade and does grade stones as such that fall within these specifications. Amongst our inventory you will not find SI3 graded diamonds, as all of ours are GIA or AGS lab graded. The more you understand these clarities and what's out there, the more you'll realize the need for a site like this.