Diamond clarity ratings are determined by the amount of inclusions and how visible they are. Inclusions consist of tiny pinpoints, markings, and clouding that will affect the overall appearance of the diamond. There are two types of flaws within a natural diamond called inclusions and blemishes. Inclusions refer to the internal flaws of a diamond and blemishes refer to external or surface flaws.
In general, diamonds with fewer inclusions and blemishes will have a better clarity rating, which will increase their brilliance and value. Diamonds with clarity grades VVS1 through SI2 have slight inclusions that may be visible to varying degrees under 10 x magnifications, but should not generally be visible to the naked eye. Diamonds with I1 clarity ratings contain inclusions that are easily seen under 10 x magnifications and may be visible to the naked eye. Diamonds with I2 and I3 clarities have major inclusions that are easily seen without magnification.