Clarity is the evaluation of a diamond's internal and external characteristics.
Being a natural, earthly material, made of pure carbon, almost all diamonds have inherent natural blemishes called “inclusions.” Three of the most common inclusions are crystals, feathers and blemishes. Crystals are minerals trapped inside the diamond and feathers are breaks in the diamond.

Blemishes are usually very small and are only on the surface of diamonds.

The size, positioning and color of these natural fingerprints determines where the diamond falls on the clarity scale. The clarity grading of a diamond is determined after examination under ten power magnifications. 

F-IF - Flawless to Internally Flawless - FL diamonds reveal no flaws on the surface or internally and are the rarest diamonds available. IF diamonds have only minor blemishes which can be removed by polishing.

 VVS1-VVS2 - Very Very Slightly Included, very difficult to see inclusions even under 10 power magnification.

♦ VS1-VS2 - Very Slightly Included, difficult to see under 10 power.

♦ SI1-SI2 - Slightly Included, after SI2, inclusions are sometimes visible with the naked eye in diamonds of larger sizes.

 I1-I3 – Very Included, has inclusions that are visible to the naked eye.

♦ I2-I3 – Inclusions drastically affect the durability and beauty of the diamond.

The fewer the number of inclusions or blemishes, the more desirable the diamond. Mimicking the shape of a pyramid, highly included diamonds sit at the bottom of the pyramid and are readily available in large quantities, making them much less expensive. The higher the diamond on the clarity scale, at the peak of the pyramid, the fewer and rarer they become, therefore, the higher the price per carat.