Like most jewels, pearls are graded based on a variety of factors. Understanding the grading system can be confusing, especially since there is no international standard. Therefore, different suppliers may grade pearls differently.
A-graded pearls are near round in shape. Many people are unaware that pearls develop in a variety of shapes and when a pearl is graded, shape is taken into consideration. Pearls graded A may appear oval, may be shaped like a drop or have other irregularities that make it not appear like a round ball. An A-graded pearl also will have fair luster, meaning that the shine of the pearl is less brilliant than higher graded pearls. An A-graded pearl will also be less than 75 percent clean on the surface, meaning there are some surface flaws that may be visible. If the pearl is on a necklace, the match to others on the strand will be fair which is another reason it receives a lower rating. In addition, the nacre rating on the pearl will be below 0.35 mm.
A pearl that is graded AA has a mostly round shape and a good luster. The surface of the pearl will have a surface that is more than 75 percent clear of blemishes or imperfections. The nacre rating, which is the substance the mollusk coats whatever it was that invaded its shell, whether it was a grain of sand or a mother-of-pearl shell bead injected by a pearl farmer. In AA-graded pearls, the nacre should be between 0.35 and 0.5 mm. Pearls in this grade are of average value while A-graded pearls are of lower value.
A pearl that is graded AAA is one of the best and most valuable types to have. It has a round shape and the luster is high. The surface of the pearl is more than 95 percent clear of blemishes and the nacre is over 0.5 mm. A thicker nacre means that the pearl was not harvested too early so that it is not prone to cracking or breaking. The pearl will also match well with others on a necklace.
When purchasing pearls, it is important to have an understanding of how the gems are graded to be sure that you are getting the quality of pearl that you want. It is also important to keep in mind that pearls may be graded differently among suppliers, so purchasing from a trusted supplier is the best way to be sure the pearls are top-quality.