The AAA-A System
This system grades pearls on a scale from AAA to A, with AAA being the highest grade, this grading scale is common to freshwater and akoya pearls only, but is accepted by many with South Sea and Tahitian pearls as well:
AAA: The highest-quality pearl, virtually flawless. The surface will have a very high luster, and at least 95% of the surface will be free from any type of defect.
AA: The surface will have a very high luster, and at least 75% of the surface will be free from any type of defect.
A: This is the lowest jewelry-grade pearl, with a lower luster and/or more than 25% of the surface showing defects. In many cases, if the pearl is being mounted into a piece of jewelry, it can be mounted so that the defects are hidden -- thus providing a lovely jewelry piece at a lesser price.
Some reputable sellers may use intermiate grades for the pearls - only those that do not fall in a category but are between two - such as A+ and AA+.
Obviously, these grading categories are quite broad and leave room for interpretation and individual judgment. Also note that in multi-pearl pieces such as strands, necklaces, bracelets, etc., all of the individual pearls may not absolutely meet the indicated grade level. For example, a strand referred to as "AAA" must have most of its pearls as AAA pearls. However, a few pearls could have slightly lower luster or a tiny bit more surface defects. This is because matching is also a primary consideration in multi-pearl jewelry, sometimes even overriding a very strict grading of each individual pearl.
