When a jeweler speaks of the clarity of a diamond he or she is referring to the amount and types of inclusions and blemishes a diamond has. Inclusions are imperfections (many like to use a nicer word "characteristics") that appear internally in a diamond while blemishes are external or on the surface of the stone. The fewer inclusions and blemishes a diamond has the "cleaner" it is. The cleaner the diamond the more expensive it becomes.

Grading diamonds for clarity should be done with either a 10x (power) loupe with a triplet corrected lens or a stereo-optic gemscope. The cleanest diamonds are the flawless and internally flawless diamonds. These stones are very rare and should really be considered investment or museum quality stones. The VVS1 and VVS2 (Very, Very Slightly Included) stones are also very clean diamonds. If the inclusions or blemishes are visible under 10x, they will be extremely small and hard to locate. Flawless, internally flawless, VVS1 and VVS2 are going to carry a high price tag and truly do not need to be considered under most circumstances.

The VS1 and VS2 (very slightly included) diamonds are excellent stones that will have very small inclusions or blemishes. Generally, these can be picked out under 10x magnification but are still hard for most people to locate. These stones make wonderful diamonds for engagement rings but will cost more than SI quality diamonds that will generally appear just as clean to the naked eye.

The SI1 and SI2 clarity diamonds are the diamonds that will suit most buyers. SI1 diamonds will have inclusions or blemishes that will be visible under 10x magnification and fairly easy to identify. SI1 diamonds are almost always eye clean and therefore really give you a great quality for a more palatable price. SI2 clarity diamonds have inclusions and blemishes that are slightly larger than SI1's and maybe visible to the naked eye, especially if on the table of the diamond or under certain lighting conditions.

I1 and lower are the end of the line in clarity grades. The Inclusions and blemishes can commonly be seen by the naked eye and are usually large.