Natts are tiny black spots caused by undigested carbon inclusions within diamonds. Black or gray material found within a diamond's internal fracture planes can also be particles or crystallographic inclusions of graphite, ferropericlase, pyrrhotite and pentlandite.
Naats are caused due to the twisting of the grain. They can be found anywhere in the diamond. They do not follow any particular pattern except in the case of Roundist Naats. They can appear singularly or collectively.