Flawless & Internally Flawless (FL & IF) diamonds have no inclusions visible under 10x magnification.
Very Very Slightly Included (VVS1-VVS2) diamonds have internal characteristics, but to such a slight degree that even a trained grader has a hard time finding them at 10x magnification.
Very Slightly Included (VS1-VS2) diamonds have inclusions more visible at 10x magnification than those in VVS stones, but they are small or few in number.
Slightly Included (SI1-SI2) diamonds have inclusions that are quite easy to see at 10x magnification, but are usually invisible without magnification when viewed face up.
Included (I1-I2-I3) diamonds have inclusions that may be visible to the unaided eye and are more obvious under 10x magnification.
Clarity is the absence of surface blemishes and internal inclusions.
Under high enough power magnification, every diamond has inclusions. Inclusions are internal characteristics that make each diamond unique, like fingerprints of nature.
To evaluate clarity, a skilled grader examines a diamond under 10x magnification and assigns a clarity grade based on the size, nature, position and quantity of clarity characteristics, their visibility and influence on durability and the overall appearance. The clarity grades range from Flawless to Included. Each clarity grade below Internally Flawless is divided into subclasses designated with a number, such as VS1 or VS2.
Because most inclusions aren't visible without magnification, clarity doesn't have much effect on a diamond's beauty. In fact, many customers maximize their budget by opting for a lower clarity grade in exchange for a higher cut or color grade. In terms of visible inclusions, the larger the diamond is, the easier it will be to see them. In diamonds under 1 carat, clarity is arguably the least important of the 4 C's. Keep in mind, some cuts hide inclusions better than others. Shapes like round brilliant, princess, cushion, oval, pear and marquise hide inclusions better than step cut shapes like emerald and asscher.