When gemologists inspect diamonds for overall quality, they must painstakingly determine the clarity of the diamond.

Using a 10x magnification loupe, gemologists determine the size, type, and position of the imperfections. Members of the industry refer to these imperfections as "inclusions." Gemologists then put the stone into one of the following classifications based on the results of their inspection:

FL-IF Flawless - Internally flawless No internal flaws or external blemishes. No internal flaws.	VVS1-VVS2 Very very slightly included. Inclusions are difficult for a trained profession to see with a 10x magnifying loupe.	VS1 - VS2 Very slightly included. Inclusions can be seen with a 10x loupe, but are not visible to the naked eye ("eye clean").
SI1 - SI2 Slightly included Inclusions are easily detected with a 10x loupe and may be detected by the naked eye.	I1 Included. Inclusions can easily be seen by the naked eye.	I2 - I3 Included Inclusions more easily visible to the naked eye.

Within the VVS, VS, and SI classifications there are additional gradations denoted by a number 1 or 2. In the case of the Included class, the subdivisions are denoted with a number from 1 to 3. Because most diamonds have flaws, stones with clarity between FL-VVS2 are considered particularly rare and are consequently particularly pricey.

We recommend selecting a diamond that has no inclusions visible to the naked eye, such as VS1 and VS2. This grade is significantly lower in price than flawless diamonds and will not contain any inclusions that would otherwise distract from the beauty of the diamond.

In some cases, cutters may choose to use certain treatments in order to improve the clarity grade of a diamond.

Laser Drill Holes: Laser drill holes are one of the few man-made inclusions that can occur inside a diamond. Drilling this type of hole into a diamond can actually raise its clarity grade. In some diamonds, the clarity grade may be determined mainly by the presence of just one or two dark included crystals in a diamond that is otherwise relatively free of inclusions. In certain circumstances, the diamond cutter will decide to use a procedure to remove the dark inclusions and, hopefully, increase the clarity of the diamond.

Fracture Filling: Fracture filling is a process that is performed on certain diamonds which have white feathers that reach to the surface of the stone. To reduce the appearance of the feather, thereby making the clarity seem higher, some cutters or jewellers will force a liquid into the diamond through this fracture. The liquid then hardens to a clear solid, filling the fracture and reducing its appearance under magnification. Because this particular type of treatment is not permanent, and because many in the diamond trade regard it as a somewhat deceptive practice, most laboratories (including GIA and AGS) refuse to grade diamonds that have been fracture filled. Jewellery 247.co.uk does not sell fracture-filled diamonds.

FL, IF: Flawless, internally flawless. No internal flaws.

VVS1, VVS2: Very, very slightly included. Very difficult to find with a 10x magnification lens.

VS1, VS2: Very slightly included. Difficult to find with a 10x magnification lens.

SI1, SI2: Slightly included. Clearly visible with a 10x magnification lens, may not see them with unaided eye.

I1, I2, I3: Included. Inclusions visible to the unaided eye.