The pearl industry do not have a universal standard for grading pearls, at this time there are two major grading systems that are in widespread use. The AAA-A system and the A-D system also known as the (Tahitian system) these are the systems most considered standard by almost all reputable pearl dealers.

The AAA-A System

The AAA-A system grades pearls on a scale from AAA to A with AAA being the highest grade, this grading scale is used for freshwater and akoya pearls only, but is accepted to be used for South Sea and Tahitian pearls as well.

AAA: The highest quality pearl, virtually flawless. The surface will have a ver high luster and at least 95% of the surface will be free from any type of defect.

AA: The surface has very high luster 75% of surface will be free from defect.

A: The lowest of the pearl grade lower luster and more than 25% of the surface shows defects.

The A-D System

Sometimes called the (Tahitian System.)
A-D system grades pearls on a scale from A to D, with A being the highest grade. This system is used to grade Tahitian pearls and South Sea pearls only.

A: The highest quality pearl, with very high luster with only minor defects over less than 10% of the surface.
B: High or medium luster. Surface has some visible imperfections no more than 30% of the surface area.
C: Medium luster with surface defects the defects should not cover more than 60% of the surface.
D: May have many slight defects spread over 60% of the surface. The imperfections should not be deep.

Both of the grading systems focus primarily on the luster and surface quality of the pearl to determine its grade. You should be absolutely certain of the meaning of all descriptive terms that may be used by retailers when buying pearls.

One thing you should know is if you are even looking at genuine pearls, are they imitation or cultured or natural pearls

How can you tell if it is an imitation pearl:

By running the pearl across your teeth the pearl will feel slightly rough on your teeth, if you feel the pearl has a smooth feeling on your teeth you are looking at an imitation pearl. Some imitation pearls are marketed as faux, simulated, artificial, and man made.